CHAPTER VI. Vertebrates

VERTEBRATES

#A. STUDIES OF FISHES#

THE LIVING FISH

Vertebrates adapted to Water Life

Materials.

Living goldfishes or other fishes in small aquaria for individual study and a few fishes in a large aquarium where they have considerable freedom of motion.

Definitions.

Trunk, the portion of the body between the head and the tail.

Compressed, a term used to describe the shape of the body when it is narrower from side to side than from dorsal to ventral surface. When the opposite is true, the body is said to be flattened.

Median fins, the unpaired fins situated on the median line, dorsal and ventral, including the tail or caudal fin, the dorsal fin, and the anal fin.

Paired fins, fins occurring in pairs of which the more anterior are the pectoral fins and the posterior are the pelvic fins.

Fin rays, the framework or skeleton of the fins over which membrane is stretched to form the fins. Fin rays are of two kinds: those composed of bone and those composed of cartilage.

Lateral line, a sense organ extending along each side of the fish in a line indicated by tubes or perforations in the scales.

Gills, respiratory organs adapted for taking oxygen from the water.

Operculum, the flaps covering the gills on each side of the head.

Pigment, a substance which gives color to an object.

Observations.

Locomotion.

1. Watch the fishes in the large aquarium and determine which fins are most used and how they are used (a) in swimming forward, (b) in swimming upward and downward, (c) in maintaining balance, (d) in remaining at rest, and (e) in guiding the movements of the fish.

2. What advantages are there to the fish (a) in the power to open and close the dorsal and anal fins, (b) in having no neck, and (c) in having a compressed form?

3. Enumerate the various ways by which the body of the fish is adapted to rapid movement through the water.

Feeding.

4. What is the food of the fishes you are studying? Feed them and watch them eat. Why is the upper jaw often called a "lip"? What is the shape and size of the mouth when opened in feeding? Does the fish chew its food? Describe in detail the fishes' method of feeding.

Respiration.

5. Identify the opercula and the gill openings. Watch the movements of the opercula and mouth, and determine what movements are concerned in breathing and their order. Describe in detail the circulation of water used in breathing and how it is caused.

Sense Organs.

6. Identify the eyes, nostrils, and lateral line. How many nostrils are there and where located? What is the position and extent of the lateral line?

7. Describe the location of the eyes. What is the shape of the outer surface of the eyes? Why this shape? Can the eyes be moved, i.e. can they be rotated, rolled, or retracted? From what direction might an enemy approach without being seen? How would such an enemy be detected?

Protection.

8. With what protective structures is the body covered? Do they hinder the movements of the fish? What are the advantages of the scale covering of fishes over the shell covering of grasshoppers or crayfishes?

9. In what other ways are the fishes you are studying protected against enemies? Since you cannot account for the red color of goldfishes on the basis of use to the fish, then how do you account for this bright color?

The Body.

10. What is the symmetry of the fish? Into what regions is the body divided?

Summary of the study of the living fish.

Enumerate in one column the different adaptations which fit the fish for life in water and in a second column state the special purpose of each adaption.

The External Structure of the Fish

Materials.

Freshly killed or preserved fish in dishes or shallow pans with enough water to prevent drying. Simple or compound microscopes, forceps, and a bristle.

Directions.

Examine the fins and identify the membrane and the supporting rods, or rays, of bone or cartilage. Notice how the ends of the cartilaginous rays keep the membrane from tearing.

Investigate the scales as to their arrangement, number, and size. Remove a small patch of scales along the lateral line to find how they are attached, where the fish's color is situated, and how access to the sensory organs of the line is permitted. Examine a scale under the microscope.

Observe the eyes and identify the parts similar to those of the human eye: lid, lash, tear-duct, cornea, iris, and pupil.

In front of and between the eyes, find the nostrils. By means of a bristle determine whether these are connected and whether they do or do not open into the mouth or the throat.

Questions.

1. Make a list of the fins, classifying them according to their structure.

2. Bearing in mind the differences in structure and consequent action,--what can you say regarding the adaptation of the several fins for protection? for rigidity or flexibility in locomotion?

3. State how much of the body is covered with scales, and where the largest and the smallest ones are found.

4. How are the scales arranged with reference to each other? What benefit is derived from this in protection? in locomotion? If you have noticed any mucus or slime upon the body, state its use.

5. Do the scales or the skin bear the pigment? Give the color pattern of the kind of fish used in class. How would this be useful to the fish in its natural home?

6. Describe the structure of a scale and state how it is attached to the skin. In what way is the lateral-line scale specialized?

7. State how, when the fish is swimming, the nostrils catch odors. By means of a diagram, with arrows show the probable direction of the water current through the nose.

8. State which of the structures of your eye are present in the fish's eye, and which are missing. Could a fish weep? wink? How would a fish sleep?

9. Inasmuch as light penetrates water but a little way, so that objects can be distinguished only within about thirty feet, would the fish be nearsighted or farsighted?

Suggested drawings.

a. A side view of the entire fish, fully labeled.

b. A bony rayed and a cartilaginous rayed fin.

c. A scale, showing its minute structure.

d. A dorsal or a lateral view of the head, showing the sense organs.

The Mouth and the Gills of the Fish

Materials.

The same materials as those used in the preceding exercise may be used here.

Directions.

The mouth, its structure and its action, can be seen by pulling the upper jaw upward and forward until the mouth and the gill chambers open fully. Examine the structure and action of the jaws, the tongue, the throat, and the teeth on each jaw and on the roof of the mouth.

Investigate the breathing apparatus from the throat side and from the exterior, noting the number, form, and structure of the gills, their attachment and their protection.

The mouth may be kept open by a short splinter or a ball of paper.

The pupil should identify the following structures:--

1. Gill, an organ for breathing the air dissolved in water.

2. Gill arch, an arch of bone or cartilage supporting the gills.

3. Gill filaments, fringe-like structures attached to the gill arches, forming the gills.

4. Gill raker, lateral projections from the gill arches.

5. Gill-slits, openings between the gill arches for the passage of water.

6. Operculum, the flap-like covering of the gills on each side of the head.

Questions.

1. Compared with the size of its body, how wide can the fish open its mouth? What do you infer as to the size of its "bite"?

2. Are the jaws rigidly affixed to the skull? Why should they be so attached, or why not?

3. Of how many pieces is the upper jaw composed? the under jaw?

4. Where are the teeth? Judging from their form, size, and situation, what do you think must be their use?

5. Do you think the tongue is used to assist in mastication? in tasting? in speech? in swallowing?

6. How many gills are there, and where are they situated? How are they attached? Which one is not free from the body throughout its length?

7. What probably causes the color of the gill filaments? What is there in their number and texture which fits them for their function?

8. What is the direction of the water current through the gill chamber? Of what use are the gill rakers?

9. How are the gills protected?

Summary.

Write a complete account of how the fish eats and how it breathes.

Suggested drawings.

a. A front view of the fish's face, with the mouth fully open.

b. A side view, as above.

c. A ventral view of the head, with both gill-chambers wide open and the gills separated from each other. Indicate currents by arrows.

d. A single gill.

The Alimentary Canal and the Circulatory System of the Fish

Materials.

Small fresh fish, shallow pans or dishes of water, forceps, and scissors.

Directions.

If the instructor has not opened the fish previously, this is to be done by the student as follows: On the ventral side, insert the scissors in the vent (in front of the anal fin) and cut straight forward to a point between the opercula. Care must be exercised in opening the chamber about the heart; this lies between the gill chambers.

The various organs, so far as possible, should be carefully drawn out and separated, in order that their structure may be distinguished.

The pupil should identify the following parts:--

1. Body cavity, the entire internal space, divided by a membrane, false diaphragm, into a large abdominal cavity and a small chamber, pericardial chamber, between the gill chambers.

2. Liver, a large red or pink mass lying at the front end of the abdominal cavity, and divided into two unequal lobes. The gall-bladder, thin-walled and green, may be seen between these lobes.

3. Alimentary canal.

a. Mouth.

b. Esophagus, in the fish a very short tube.

c. Stomach, white and muscular, beginning with a very short esophagus and ending as a blind sac. If it is much distended, open it to see what the fish may have eaten.

d. Small intestine, thin-walled, tubular, and somewhat coiled.

e. Large intestine, a short, thin-walled expansion at the posterior end of the small intestine; usually less than half an inch long.

f. Coeca, from two to several small pouches attached where the small intestine leaves the stomach.

4. Spleen, a reddish brown globule between the folds of the intestine.

5. Swim bladder, an elongated chamber lying against the backbone, partitioned off from the cavity below by a delicate membrane.

6. Peritoneum, the delicate, silvery membrane which lines the abdominal cavity and enfolds the viscera. Note its spots of pigment.

7. Pericardial chamber, the chamber around the heart; see § 1 above.

8. Heart. As the fish is placed belly upward in the pan the ventricle faces you, pink, conical, and muscular. Posterior to it, on the dorsal side, is the auricle, a membranous sac.

9. Ventral aorta, arising on the anterior surface of the ventricle as a white muscular "cord" (really a tube) which is enlarged close to the heart into a bulb, the arterial bulb. You should follow up this aorta until you see it divide right and left to send its branches outward into the gills, the branches being called gill arteries.

Questions.

1. The fish frequently swallows its food alive. Why should the stomach be muscular? Why is it better that the intestine does not leave the stomach at the end opposite the esophagus?

2. Of what use can the coeca be? What structure of the human intestine do you recall that is at all like them in form or use?

3. How many times the length of the body is the length of the alimentary canal? Does this indicate that the fish is compelled to eat a great deal of poor food or that its food is highly nutritious, so that little need be taken?

4. Near which end of the fish's body is the heart? Is this the usual or the unusual condition among animals you know about? What advantages can you think of in this arrangement?

5. What advantages are there in having the heart in a chamber separated from the other vital organs?

6. Of how many chambers does the heart consist? Why should at least one of them be muscular?

7. How many times does the blood pass through the heart in making a complete circuit of the body? Would you call this a single or a double circulation?

8. Does the heart force the blood onward or does it draw blood into itself, i.e. is the heart a force pump or is it a suction pump?

9. How is circulation made complete? If the heart is a force pump, is its power sufficient to drive blood through artery, capillary, vein, and into auricle, if the capillaries can stand the pressure, or is another action concerned? If it is a suction pump, why does the blood leave the heart?

Suggested drawings.

a. The body cavity, with viscera undisturbed.

b. The alimentary canal extended.

c. The anterior end of the fish with the sinus held open, to show the general situation of the parts.

d. The heart in its chamber, with the outgoing vessels as far as dissected. Use arrows to show direction of circulation.

e. A copy of some good diagram or chart which illustrates the heart of the fish with the connecting veins and arteries.

Fishes: A General Review and Library Exercise

1. Food and the feeding habits of young and of adult fishes.

2. The diet and habits of cod; lantern-fish; swordfish; ramora; hagfish; angler; gar-pike; sturgeon; shark; sawfish; paddle-fish.

3. The variations, real or apparent, in the breathing habits of the porcupine-fish; the climbing-fish; the lung-fish.

4. Peculiarities in swimming as seen in the flying-fish; the flounder; the sea-horse.

5. Intensity of sound under water, and the corresponding structure of the fish's ear.

6. Light and sight under water (as in 5).

7. Protection of fishes: sting-ray; torpedo; coral-fish; sturgeon; lava-fish; swordfish; sawfish; pipefish.

8. The social instinct of fishes, and "schools."

9. The breeding habits of salmon; eel; stickle-back; sturgeon; whitefish; shark; sea-horse; sunfish.

10. The fishing industries of the Great Lakes or of the cold oceans, with a list of the fishes caught and their values.

11. Fish nets and traps: seine; gill-net; pound-net; trawl, French or English; fish-wheel; fish-weir; spear; dip-net; set-line; spoon; fly.

12. The U.S. Bureau of Fisheries: its locations, its problems, and its methods.

13. The State Fish Commission, as above.

14. Game and fish laws; their purpose and their enforcement.

15. Game fish of the fresh waters; trout, bass, pickerel, and muskellunge.

16. Game fish of the ocean: tarpon, tuna, sea-bass, swordfish, and bluefish.

17. Fish as food.

18. Fish diet and leprosy.

19. Fish diet and parasitic worms.

20. Fish nuisances: carp, catfish, and dogfish.

21. Commercial products of fishes, their preparation and their uses: caviar, shagreen, cod liver oil, isinglass, and glue.

22. The geographic distribution of fishes, with means of dispersal and restriction.

23. The faunal regions of the lake (or ocean), with characteristic forms.

24. Fishes of ancient times; of the Devonian period.

25. The story of the early life of Louis Agassiz; of D. S. Jordan; of C. H. Eigenmann; of Bashford Dean.

26. Goldfish: their origin; how to care for them.

27. Fashions in fish tails, old and new.

28. Development and variation in scales; fashions in scales.

29. The common orders of fishes, with examples.

Primitive Chordates

Materials.

An acorn-tongued worm, a lancelet, a lamprey, a shark, and a perch. If individual specimens are not available, the pupil's text-book and charts are to be used.

Observations.

Acorn-tongued worm: Notice the very simple form and structure of the symmetrical body, the "proboscis," the collar surrounding the neck with its simple rod of cartilage, the marks of internal gills and gill slits extending some distance along the body, and the presence or absence of sense organs. The acorn-tongued worm (Balanoglossus) lives in the sand of the seashore and in shallow water in temperate and tropical regions.

Lancelet: Observe the form of the body, of the fin, and of the mouth; note the presence or absence of sense organs, and find out the number of gills or gill slits. The lancelet (Amphioxus) is similar in habit to the acorn-tongued worm. By day it lies buried with only the mouth exposed, but at night it swims actively about. It is somewhat more confined to the tropics.

Lamprey: Observe here also the primitive or unspecialized form of the body, of the fin, of the jawless mouth, the number of gill slits, and the sense organs.

Shark: Examine the body, noting its form and differentiation into regions, its covering, its fins, mouth, gill slits, and sense organs.

Perch: If you have not already studied the bony fish, the points suggested for the shark will be sufficient for this exercise.

In each case, find out the condition of the skeleton.

Questions.

1. Which of these animals seem most simple in form, and which most complex? Give a reason for your answer.

2. Give the stages which show how the fold of skin develops into separate fins.

3. How does the number of gills and gill slits change in the series? (Give definite numbers.) How may the reduction in the number of gills be compensated for in the amount of surface exposed for the exchange of gases in breathing?

4. How is protection afforded the delicate structure of the gills in the final form?

5. Give the stages in the formation of a definite, symmetrical mouth with jaws of equal size.

6. The presence of sense organs may be taken to indicate that there is an organ of control, or brain. How is the development of this organ like or unlike that of the other structures in the series?

7. For the developing brain and nervous system what protection and support is afforded in each case?

The foregoing questions may be answered in tabular form by arranging the names of the animals in a line and the questions in a column.

Suggested drawings.

a. Acorn-tongued worm, × 1.

b. Lancelet, × 1.

c. Lamprey, × 1/2.

d. Shark: 1, head as far as the pectoral fins; 2, the tail.

e. Perch, as directed for shark.

#B. STUDIES OF AMPHIBIA#

#Progress from Water-living Animals to Land-living Animals#

The Living Frog or Toad

To show how an Animal may be adapted to both Land and Water Life

Materials.

Living frogs in small cages or aquaria; living toads; some pungent liquid, as ammonia.

Observations.

The Body.

1. Contrast the body of the frog with that of the fish as to regions, shape, and compactness. How do you account for the differences?

Locomotion.

2. What kinds of locomotion can a frog use? Why is it difficult for a frog to crawl or walk? How far can a frog jump? How are swimming and jumping accomplished? What do you think is the use of the "hump" on the back?

3. Identify in the legs the thigh, shank, ankle, foot, toes, and web, and in the arm, the upper arm, forearm, wrist, hand, and fingers. State in detail the differences in structure and in position between the fore and hind limbs. How do you account for these differences?

Feeding.

4. Induce a frog or toad to eat by dangling food, such as a piece of raw meat or meal worms, small earthworms, etc., before it. How does it seize the food? What will it eat? How is the mouth adapted to this manner of feeding?

Respiration.

5. The frog has no diaphragm, and therefore no chest cavity; watch very carefully the movements of the mouth, the nostrils, the throat, and the sides of the body to determine how the problem of breathing (how the air is gotten into and out of the lungs) without a diaphragm is solved. Write a detailed account of the frog's method of breathing which shall explain just how the air is forced into the lungs.

6. What would be the effect of propping open the mouth of the frog? Why? Does the frog breathe in the usual manner while under the water? If not, how do you explain its ability to remain under water for a long period of time?

Sense Organs.

7. Investigate the efficiency of the five special senses in the frog by devising experiments to test each sense; as, for example, giving a frog its liberty on the floor and trying to catch it again, to test the sense of sight. Write an account of your experiments and their results. Which of the senses is best developed? Give reasons for your answer.

8. Compare the eye of the frog with respect to its shape, movements, parts, and protective structures with that of the fish. In what respects are they similar? in what respects different? Why should they differ?

9. Where are the frogs' ears located? What do you think of the efficiency of an eardrum situated on the surface of the body? Why?

10. The frog has certain other responses. Try turning the jar or cage containing a frog around to face the frog in another direction. What happens? How do you explain this response on the basis of use? What other responses have you noticed?

Protection.

11. Has the frog an exoskeleton? Describe the color scheme of the frog and explain how it may be protective. Why are frogs brighter in spring than in fall?

12. Why do frogs usually live near water? Do they ever leave the vicinity of streams? If so, when?

Summary.

In what ways is the frog adapted to water life? In what ways to life on land? In what respects do toads differ from frogs?

The Frog's Mouth

Materials.

Preserved or freshly killed frogs in dishes or shallow pans of water; forceps and a bristle.

Observations.

Open the frog's mouth as widely as possible and, if necessary, insert a splinter to hold the jaws apart. Identify the following structures:--

Tongue. Draw it forward until the free end extends from the mouth and is outspread; observe its form, extent, and attachment.

Teeth. Find those on the jaws and on the roof of the mouth.

Nostrils. Push the bristle inward through a nostril to determine its direction and extent.

Vocal cords. These form a hard white mass in the floor of the mouth, well back behind the tongue.

Glottis, the slit inclosed between the vocal cords, opening into the trachea.

Esophagus, the passage to the stomach, at the posterior end of the mouth.

Eustachian tubes, small passages outward to the ears at the junction of the upper and lower jaws.

Questions.

1. Describe the probable action of the frog's tongue in catching a bug.

2. What advantage can you ascribe to the peculiar mode of attachment of the tongue?

3. Of what use is the notch in the inner end of the tongue? (Note its position when the tongue lies at rest in the mouth.)

4. If the frog chewed its food, how would the existing structure of the nostrils be very inconvenient?

5. Recall either the frog's habit of feeding or the structure of the nostrils. Do you think the nostrils are of much service in smelling? State the reason for your answer.

6. Of what use are the vocal cords and why are they so muscular? Consider their use in sound making and also their condition during swallowing.

7. Of what use are the teeth? Recall the form and use of the fish's teeth.

Suggested drawings.

a. The mouth, wide open and with tongue extended.

b. A diagram showing the path of air and of food through the frog's mouth.

The Organs of Digestion, Absorption, and Excretion

Materials.

Freshly killed or preserved frogs in dishes or shallow pans of water, forceps, and, if the pupil is to do any dissecting, scissors.

Directions and Observations.

The specimens may have been opened by the teacher, or may be dissected by the pupil as follows:--

Placing the frog on its back, with forceps firmly grasp the skin of the abdomen and the muscles beneath, just in front of the hind legs, and with the scissors cut straight forward in the middle line until the floor of the mouth is reached; this will separate the arms. Care must be taken not to cut too deeply, but this may be avoided by keeping the skin uplifted. Now cut sidewise in front of each hind leg in order that the body wall may be laid aside. Under the arms the heart will be seen; it will be studied as a part of the circulatory system.

* * * * *

Identify the following organs:--

Liver, the large red or brown mass, consisting of several divisions and lying close up under the arms.

Bile sac, small, green, and between the liver lobes.

Alimentary canal.

1. Mouth.

2. Esophagus.

3. Stomach, the elongated, light-colored, firm, and muscular portion.

4. Small intestine, a slender, more or less closely coiled, tubular portion.

5. Large intestine, a thin-walled enlargement at the posterior end of the canal.

6. Duodenum. This is a muscular portion of the small intestine immediately following the stomach, against which it is folded.

Pancreas, a yellowish, pulpy mass lying in the fold between the stomach and the duodenum.

Spleen, a dark red globule, usually smaller than a pea, lying nearly free among the folds of the small intestine.

Fat bodies, yellow fringe-like structures, sometimes found near the stomach.

Kidneys, a pair of elongated dark red organs, behind the spleen and against the back. Note their numerous blood vessels. Possibly the ureters, or urinal ducts, can be discovered and traced to their junction with the bladder, a clear membranous sac in the posterior extremity of the body cavity.

Peritoneum, a thin membrane lining the body cavity and attaching the vital organs to the backbone.

Note.--Specimens secured in late fall, winter, or early spring may contain, if female, a large number of dark-colored eggs; or if male, two white testes, located near the kidneys and similar to them in form, though smaller.

Questions.

1. Name the parts of the frog's alimentary canal.

2. Name the glands or organs which are accessory to the canal.

3. How long is the esophagus? How does the presence or absence of a neck affect the esophagus?

4. How does the thickness of the stomach wall compare with that of the intestine, and how do you account for the difference?

5. Measure the length of the trunk of the frog's body and that of the outstretched alimentary canal. How many times the length of the one is that of the other? How does this ratio compare with that of an herbivorous animal? (The sheep's food canal is about thirty-two times the length of its body.)

6. What is the color of the bile, as seen through the walls of the bile sac? This color is characteristic of carnivorous animals; in herbivorous forms it is yellow. Find its color in some omnivorous form, as man.

7. Name the organs concerned in excretion.

8. What holds the internal organs in place, and from what are they suspended?

9. The spleen is called a "ductless gland." Give its function, and explain why a duct is not necessary to it.

10. Since the frog swallows its food alive and entire, what work must the stomach do? What digestive organs would be absent from the mouth, or else poorly developed?

11. Since the frog is carnivorous, what digestive ferments are probably present, and what ones absent from the alimentary canal?

12. Fat bodies are largest in the fall, and are rarely found in the spring. How can you account for this?

13. When through with the general study of the alimentary canal, you may open the stomach by cutting it lengthwise. Describe the character of the stomach lining as to folds and villi, stating the advantage of each being present and the reason for the direction of the folds. Tell how the food is propelled onward through the alimentary canal. Give the scientific name for this action.

Suggested drawings.

a. The viscera (internal organs) undisturbed.

b. The alimentary canal extended.

c. The excretory system.

The Organs of Circulation and Respiration of the Frog

Materials.

The materials used in this exercise are the same as those used in the preceding exercise.

Observations.

The pupil should identify the following structures:--

Pericardium, a membrane that surrounds the heart and, in the case of the frog, separates the body cavity into two portions, the abdomen and the pericardial chamber.

Heart, lying between the shoulders and in front of the false diaphragm. It is conical in form and composed of three chambers.

Ventricle, the pink, conical, and muscular portion of the heart, pointing backward and outward.

Auricles, right and left. These are anterior and dorsal to the ventricle, thin, membranous, and dark-colored.

Arterial trunk, the single large blood vessel, usually empty of blood, and white. Note its origin and trace it as far as possible, at least until you see it divide to encircle the throat.

Sinus venosus, a large membranous sac dorsal to the heart and connected with the right auricle.

Lungs, two small oblong, pink, spongy sacs, lying between and behind the shoulders.

The pupil may also identify the following structures if a specimen is available which has the blood vessels injected.

Conus arteriosus, or "arterial trunk," a large artery passing obliquely forward from the ventricle, and dividing into three branches on each side.

Carotid arteries, the first branches of the conus, to the head and neck.

Aortas, the second branches of the conus, to the dorsal region.

Pulmocutaneous arteries, the third branches of the conus, to the lungs and skin.

Dorsal aorta, the large artery along the back, formed by the union of the two aortas.

Iliac, or femoral arteries, the two posterior divisions of the dorsal aorta, supplying the legs.

Posterior (ascending) vena cava, a large vein close to the dorsal aorta, passing forward from the kidneys.

Hepatic veins, large veins connecting the liver with the posterior vena cava.

Anterior (descending) venæ cavæ, large veins formed by the junction of the veins from the arm, neck, and head on the right and left sides.

Subclavian veins, from the arms.

Jugular veins, from the neck.

Questions.

1. Of how many chambers does the frog's heart consist? Name them, and describe them as to size, color, and structure.

2. Which chamber receives blood from the body, and which receives blood from the lungs?

3. Name the large arteries and give the regions which they supply. Name the large veins and give the regions from which they come.

4. Describe the lungs as to size, both when inflated and when uninflated. Describe their color; entirety or subdivision; texture.

5. In the inflated lung, notice the interior partitions or chambers, which are called vesicles. How do they affect the amount of surface exposed for gas exchange in breathing?

6. Measuring the lung collapsed and again when inflated, calculate its approximate volume in each case and state how much air it may take in during an inspiration.

7. Describe the diaphragm and state its probable use as a factor in respiration or as a partition.

Advanced questions.

8. Apparently the pure and the impure blood must commingle upon entering the single ventricle, but by a simple device this scarcely occurs. How would such commingling affect the purity of the blood as it reached the tissues, and hence affect waste removal, oxidation, body temperature, activity, and intelligence?

9. What are the chambers of the fish's heart? of the mammalian (human) heart? How may the heart of the frog be regarded as intermediate between these others? How and where might the growth of a partition within it bring about the higher structure? (This actually occurs in certain reptiles.)

10. The lungs are said to be outgrowths of the alimentary canal. Explain how their connection would tend to show this.

Suggested drawings.

a. The heart and lungs in their normal position.

b. The circulatory system, as seen in the injected specimen.

c. A copy of the diagram or model of the circulatory system.

d. A diagram of the respiratory tract from the nostrils to the lungs, by arrows showing the course of the air.

The Nervous System of the Frog

Materials.

Specimens which have the brain exposed and other specimens whose viscera have been removed so that the spinal nerves can be seen; pans or shallow dishes of water and forceps.

Observations.

The nerve tissues are generally white in color unless they have been specially treated and stained. The pupil should identify the following structures:--

A. Brain, those enlargements of nerve tissue situated in the head and composed of four principal parts, as follows:--

1. Cerebral hemispheres, a pair of elongated lobes, the anterior enlargements.

2. Mid brain, or optic lobes, a pair of large ovoid structures, projecting diagonally forward and sidewise.

3. Cerebellum, a slender, transverse ridge, close behind the midbrain.

4. Medulla, the anterior end of the spinal cord, widest in front and containing a triangular depression.

(Frequently a pair of smaller enlargements is to be seen in front of the cerebral hemispheres; they are the olfactory lobes, and from them nerves pass forward to the nasal chamber.)

B. Spinal cord, extending along the spine, giving rise to nerves.

C. Spinal nerves, ten pairs of nerves which are connected with the cord through dorsal (sensory) and ventral (motor) roots, and which penetrate the body and its appendages. The first enters the neck; the second and third join and enter the arm; the fourth to sixth penetrate the skin and muscles of the trunk; the seventh to ninth join by a plexus to form the sciatic nerve which supplies the leg, and the tenth enters the posterior portion of the body.

Questions.

1. Which lobes of the brain are paired? Give at least two possible causes or reasons for their double structure.

2. The optic lobes are connected with the eyes. Compare their size with that of the other parts. Of how much use do you think they are to the frog?

3. If folds or convolutions in the surface of the cerebrum indicate intelligence, thoughtfulness, or mind, what do you infer as to the frog's mental condition and power to think?

4. Has the frog brain or "brains"? Explain.

5. Name several things done by an animal's brain.

6. Which of the spinal nerves are specially large? Why should they be large?

7. What advantages are there in the frog's having a dorsal nerve cord instead of a ventral one, as the earthworm has?

What would be the effect of cutting or breaking the dorsal root of a spinal nerve? the ventral root? the entire spinal cord? How do you explain the convulsions of the brainless (beheaded) chicken or frog?

8. What kinds of impulses originate outside of the nerve center, and what kinds in the center?

9. Sensations reach the cord and brain through the dorsal root of the spinal nerve. What kinds of messages travel through the ventral root, and in what direction do they go?

Suggested drawings.

a. The brain.

b. The spinal cord and its nerves.

c. The nervous system.

d. A diagram of the cord and its nerves, showing the kinds and the directions of the nerve impulses.

The Endoskeleton of the Frog

Materials.

Prepared frog skeletons mounted in glass-covered boxes or in other cases suitable for individual study; other vertebrate skeletons for reference.

Observations.

The pupil should examine his specimen and identify the following structures:--

A. Skull:--

1. Cranium, or brain case, the central and hinder portion.

2. Nasal bone, a triangular bone lying in front of each large opening, or eye orbit, and attached to the anterior end of the cranium.

3. Premaxillaries, a pair of small bones which form the tip of the nose.

4. Maxillary, a slender bone forming the side of the upper jaw.

5. Dentary, the bone of the lower jaw, corresponding to the maxillary.

6. Occipital foramen, the posterior opening or entrance into the cranium, normally covered dorsally by cartilage and most easily seen in a separate skull.

B. Vertebral Column:--

1. Cervical vertebra, the first vertebra, supporting the skull.

2. Dorso-lumbar vertebræ, vertebræ with small lateral processes.

3. Sacrum, the ninth vertebra, bearing extra long lateral processes or "arms."

4. Urostyle, the last vertebra, lying in the median line, a long, slender, blade-like bone, really formed by the fusion of several vertebræ.

C. Vertebra:--

1. Centrum, the solid, nearly circular portion.

2. Lateral process, one of the paired projections, extending outward on either side.

3. Neural spine, the single projection, extending toward the dorsal side.

4. Neural arch, formed largely by a connection between the lateral process and the neural spine. The arch above and the centrum below inclose the neural canal.

D. Pectoral, or Shoulder, Girdle:--

1. Sternum, the "breastbone," extending along the median ventral line.

2. Coracoid, a heavy bone extending from the sternum sidewise to support the arm.

3. Clavicle, the "collar bone," a light bone in front of the coracoid.

4. Scapula, the "shoulder blade," a broad, thin bone which arches around to the dorsal side.

E. Pelvic, or Hip, Girdle:--

1. Ilium, a long, slender, curved bone, with its mate uniting to form an inverted "wishbone"; it is joined to the sacrum.

2. Pelvis, the region of the socket at the junction of the ilia.

F. Fore Leg, or Arm:--

1. Humerus, the single bone of the upper arm.

2. Radius, the bone of the lower arm on the thumb side; in the frog united to the ulna.

3. Ulna, the bone of the forearm opposite the radius.

4. Carpals, small bones of the wrist.

5. Metacarpals, a single series of long bones forming the palm of the hand.

6. Phalanges, the bones of the fingers and thumb (singular phalanx).

G. Hind Leg:--

1. Femur, the thigh bone, next to the body.

2. Tibia, the larger bone of the lower leg on the inner side; in the frog united to the fibula.

3. Fibula, the smaller bone of the lower leg.

4. Tarsals, the small bones of the instep.

5. Metatarsals, the long bones of the instep.

6. Phalanges, the bones of the toes.

Questions.

1. Whereabouts in the frog has nature made an attempt to inclose delicate or vital structures in bony cases?

2. Examining the inside of the mouth, find the teeth. Judging from their size and structure, of what use are these teeth?

3. What advantages can you see in having the arms and legs attached to girdles instead of having them fastened directly to the vertebral column? How has their development affected the shape of the trunk, as opposed to that of the fish?

4. Make a comparison of the two girdles as to their attachment to the spine and their consequent rigidity or freedom of movement.

5. How many vertebræ are there in the spinal column? What advantage can you see in having the column composed of many small vertebræ instead of a few large ones? Enumerate those having a special form or structure, and state the use of each.

6. On the vertebræ notice any irregularities, prominences, or roughenings. For what are such bones better adapted than smooth bones would be?

7. How is the frog's humping permitted? How are the urostyle and the pelvis connected, if at all? Has this any effect on motion? (See living frog.)

8. In parallel columns, keeping corresponding parts in a line, tabulate the bones of the fore and hind limbs.

9. State how extra length has been attained in the hind leg, and give the purpose or the result of this lengthening.

10. In the forearm notice the fusing of the radius and ulna. How would these parts act in rotating the hand, as compared with your own, where they are free? Compare also the tibia and fibula. Where in the frog's leg is turning made possible by the use of parallel bones?

11. Compare the frog's hand and foot as to number of fingers and toes; as to length and spread. Have any fingers or toes only two phalanges?

12. How would an inner skeleton affect the growth and the size of an animal, as compared with an outer skeleton, like the clam's?

13. How would the lack of an outer skeleton influence sensitiveness, activity, and intelligence?

Suggested drawings.

a. The skull and trunk, with appendages of one side.

b. Each set of bones separately, as the skull, the column, etc.

Comparative Study of Amphibia

Materials.

Various amphibia, either dead or alive, such as newts, mud puppies (necturus), salamanders, and several species of frogs and toads, especially tree toads.

Observations.

Answer the following questions with respect to each animal:--

1. What regions of the body are present? What is the general shape and size of the body?

2. For what kind of locomotion are the limbs fitted? How?

3. Have the hands and feet any special adaptations? If so, what are they and for what purpose?

4. With what organs does the animal breathe? If with gills, are they external or internal?

5. Judging from the specimen, what do you think is the habitat? Give reason for your answer.

Summary from the Comparative Study of Amphibia

1. Which of the amphibia in this study are fish-like in character? What are the fish-like characters? Do you think these fish-like amphibia are of a lower or higher type than the others? Give reasons for your answer.

2. Show how the variation in (a) the form of the body, (b) color patterns, and (c) the structure of the legs and arms of the amphibia are related to habitat and mode of life.

Amphibia: A General Review and Library Exercise

1. The usefulness of the American toad.

2. The breeding habits of the common frog; of the Surinam toad; of the obstetrical toad; of the "smith."

3. The development of the axolotl.

4. The habits of the tree frogs and their variable coloration.

5. The croaking of frogs and of toads.

6. The flying frog of Ceylon.

7. The distribution and habits of the hellbender; of the mud puppy; of the Congo "snake."

8. The general absence of the amphibia from arid regions.

9. Frog farming for city markets.

10. Protective devices of various amphibia.

11. Toads and warts.

12. The homing and water instincts of toads.

13. Hibernation, seasonal or prolonged, of toads and frogs.

14. The changes in the respiratory and circulatory system during metamorphosis.

15. Ontogeny and phylogeny, as illustrated by amphibia.

16. The structural defects which would prevent an ambitious frog from becoming a highly trained and skillful animal.

17. The classification of amphibia, with examples.

18. The kinds of frogs and toads found in the region where you live.

#C. STUDIES OF LIVING REPTILES#

#Showing Diversity of Adaptation among closely related Animals#

The Snake

1. What is the shape? What regions are present? How do you distinguish between the trunk and the tail? Has the tail any use? What are the advantages of a body without limbs?

2. Describe the snake's path in locomotion. How is locomotion accomplished? Is the absence of limbs a hindrance to the animal in its locomotory activity?

3. Describe the appearance and movements of the tongue. Of what use are these movements of the tongue?

4. What evidence is there that the snake breathes with lungs?

5. What sense organs do you find? Compare the ears and eyes with those of the frog. What explains the peculiar staring appearance of the eyes?

6. What is the color scheme? Does it appear to be protective? If so, how?

7. Of what does the exoskeleton consist? How are the scales arranged? What variations in the size of the scales do you find? What special use have some of the scales? How fitted for this? How does a snake moult? Appearance before and after moulting.

The Florida Lizard

1. Describe the body as to regions and shape. Is the tail of use?

2. What are the lizard's locomotory abilities? How is it fitted for living in trees?

3. Feed the lizard flies or meal worms and describe its method of capturing them.

4. Compare the lizard's respiration and sense organs with those of the snake and frog.

5. What is the usual color of the lizard? What have you discovered about its power to change colors? How may this be of use to it?

6. Of what does the exoskeleton consist? Is the entire body covered? How are the scales arranged? How does the lizard moult?

The Turtle

1. In what important ways does the body of the turtle differ from those of the snake and lizard?

2. What methods of locomotion has the turtle? For which method is it best fitted? How? Why are its movements in water so much less clumsy than on land? (Compare weight on land with weight in water.) Compare the efficiency of the locomotion of a turtle with that of a lizard and suggest a reason for the difference.

3. What do turtles eat while in the laboratory? Since turtles have no teeth, how can they bite off their food?

4. What can you discover with respect to the respiration of the turtle? Does it breathe when under water?

5. What sense organs has a turtle? Which appears to be most highly developed? How do you know?

6. In what various ways is the turtle protected against enemies? (You should state several.) Are you afraid of a turtle? If so, why? Why does the turtle need more protection than the snake or lizard?

7. Describe the color pattern of the turtle you are studying. Is this arrangement of colors the same for others of the same species?

8. Describe the arrangement of the epidermal plates of the turtle's shell. Are the arrangement, number, and form of plates the same for all turtles of this species? Compare with the plates of other species. What variations do you find?

Reptiles: A General Review and Library Exercise

1. Characteristics of reptiles.

2. Orders of reptiles. Characteristics and examples of each order.

3. Poisonous snakes found in the United States. The poison fangs of a rattlesnake. Habits of the rattlesnake.

4. Cures for snake bites, fabled and real.

5. Snake charming.

6. Famous poisonous snakes and their habits.

7. The characteristics and habits of alligators.

8. The characteristics and habits of marine turtles. How they differ from pond turtles.

9. For what is each of the following noted? Where does it live? The terrapins? the horned toad? the Gila monster? the chameleon? the glass snake?

10. Reptiles of former (geological) times compared with those of the present.

11. Care of eggs and young. Swallowing of young by snakes.

12. Food of snakes. Defend the proposition that non-poisonous snakes are beneficial and should not be killed wantonly.

13. Investigate and write an account of the economic value of reptiles.

#D. STUDIES OF BIRDS#

#Vertebrates specialized for Flight#

The Living Pigeon

Materials.

Living pigeons in cages, and, if practicable, other birds such as chickens, canaries, and sparrows.

The Body.

1. What divisions of the body are present? Compare the relative size of these divisions with that of other vertebrates studied. Can you account for the great increase in bulk of the trunk over the other divisions? How do you account for the longer neck?

Flight.

2. What is the shape of the body? How is the body made smooth? To what is the shape and smoothness adapted? (Recall the appearance of a plucked pigeon or chicken.)

3. Observe the size of the wings by measuring their width and spread (measured from tip to tip when outspread). Where on the body are they attached? How is this point of attachment advantageous? What is the shape of the upper surface of a wing when spread? of the lower surface? How is this shape advantageous in flight?

4. Where are the largest and strongest feathers? How are they arranged with respect to each other: (a) to prevent air passing through on the down stroke of the wing? (b) to permit folding?

5. What is the shape and width of the tail when outspread? when folded? In what way does the tail assist in flight?

Walking and Perching.

6. Identify the parts of the leg as in the frog. (See study of frog.) With what exoskeletal structures is each part covered? How many toes are there? Does the pigeon walk on its foot or on its toes? Where is the ankle joint?

7. The bird's legs are arranged to support the body. How is this brought about? Compare with the lizard and frog in this respect.

8. Explain how the legs are adapted (a) to preserve the balance of the body, and (b) for perching. Are they well or poorly adapted for locomotion? Explain. For what other purposes are the legs sometimes used?

Feeding and Drinking.

9. What is the form and character of the jaws of the pigeon (called the beak)? Offer food, and watch the pigeons eat. How does a pigeon seize and swallow food? Does it chew the food? Locate the crop. If the pigeon chewed its food, would it have a crop? Why? How does a pigeon drink? How does the chicken drink?

Respiration.

10. What parts move in breathing?

11. Compare roughly the body temperature (by touch) of man, the pigeon, and the frog. Which has the highest temperature? which the lowest? How can you account for the higher temperature of the bird? (Which of the three must be able to endure long-sustained effort? What is the effect on your own body of long-continued effort?)

Sense Organs.

12. Identify the eyes, ears, and nostrils, and describe their location. What are the advantages in having the eardrum at the bottom of a canal? Is there any disadvantage? What is the probable function of the inner thin eyelid? How does it work?

13. Investigate the power of response of the special senses. Which seems to be the most alert? State the experiments which you used and your reasons for your answers to this question. Which senses are most serviceable in finding food? in protecting against enemies?

Protection.

14. In what different ways are feathers protective to the bird? Study the arrangement of the feathers to find how protection is increased in this way. How do the feathers and parts of feathers which lie next the body differ from those which are on the outer surface? What parts of the body are unprotected by feathers? How are these protected, if at all?

15. Note the flexibility of the neck. Through what part of the arc of a circle can the pigeon turn its head? How is this especially important to birds?

16. What means of defense has the pigeon when attacked?

Summary.

1. Make a list of the important adaptations of the pigeon, (a) to flight, (b) to feeding, (c) to perching, and (d) to protection.

2. Which is the most highly specialized, the fish, frog, snake, or bird? Give reasons for your answers.

3. In what various ways are feathers of use to the bird?

Suggested drawings.

a. Side view of the head.

b. A foot.

c. A wing.

d. Side view of the pigeon.

Supplementary Studies of the Pigeon

These topics and questions should be answered from experience with pigeons and observations of their habits and behavior, and from books to be obtained from the school and public libraries.

1. The homing instinct of the common blue pigeon and of carrier pigeons.

2. Nesting habits, number of broods and number of young in each brood, feeding the young. Why is this method of feeding the young necessary?

3. Varieties or breeds of pigeons. How the various varieties were produced; how they are kept true; reversions of type.

4. Darwin's experiments with the pigeons; object of the experiment. Whitman's experiments.

The Exoskeleton of the Bird: Plumage

Materials.

Living birds, as perhaps pigeons, or mounted or stuffed skins, separate feathers, portions of feathers, microscopes.

Observations.

The pupils should study the arrangement of the feathers and their variations in form and size, and should identify the following principal kinds:--

Contour feathers, those feathers, generally broad, which cover the body, giving to it its outline and color.

Coverts, those feathers which cover joints, such as the joints of the wing and tail.

Primaries or pinions, the long stiff feathers of the outside of the wing, used in sustaining the bird in flight.

Secondaries, the shorter, more symmetrical feathers lying next and over the primaries.

Down, soft feathers found on young birds and next to the skin on some adults.

Thread feathers, best seen about the eyes, ears, and beak.

Quill, the bare stiff portion, one end of which is inserted in the skin. Examine its internal structure.

Vane, the broad expanded portion, the part ordinarily seen on the bird.

Shaft, the mid-rib of the vane.

Barbs, the delicate outgrowths of the shaft making up the vane.

Barbules, the subdivisions of the barbs, some of which are provided with hooklets. These may well be studied microscopically.

Questions.

1. How is the plumage arranged to offer least resistance to the air in flight? How does a bird sit when exposed to the wind?

2. In a column write the names of the parts of a feather, and opposite each part state its particular use.

3. Of what use are the hooklets on the barbules?

4. State and explain the peculiar position of the shaft of the primary feather; of that of a contour feather.

The plumage of many birds contains all stages of feather specialization, from down to pinion. Find as many of them as you can on your specimen.

5. What reason can you assign for the fluffy base and the compact end of the contour feather?

6. How much of the feather of a full-grown bird seems to be supplied with blood vessels? How does this bloodless or full-blooded condition affect the weight of the feather; of the plumage; of the bird?

7. How would the above condition affect the temperature of the blood and of the body? Would it tend to cool the animal or to conserve its heat?

8. Show how the air lying motionless amongst the plumage may serve the same purpose as that in the packing of a fireless cooker or a "thermos bottle."

9. How would the above condition affect the growth and repair of the feather? What connection has it with moulting?

10. What kind of feathers forms most birds' "baby clothes"? What kind forms the adults' "underclothes"?

Suggested drawings.

a. A typical feather.

b. A feather of each kind.

c. A bird with wings outspread, showing positions of feathers.

d. The minute structure of a feather.

Birds and Migration

To illustrate Distribution

Work in the Laboratory

Materials.

Bird skins or mounted birds, at least one representative of each order and, better still, of each family of the birds which pass through or remain in your neighborhood; specimens in a museum may also be used. Some guide to the identification of birds, as Walter's "Wild Birds in City Parks" or Reed's "Bird Guide." A good diagram of a bird.

Directions.

Your object here is to familiarize yourself with the appearance of birds of different types, and with the terms used in describing them. Study first a diagram of a bird and learn the terms and their applications.

An important item in the description of a bird is its length. This is obtained by measuring from the tip of the beak, over the curve of the head, to the end of the tail. This measures a curved line and gives a greater length for a bird than the straight line you would naturally estimate. Train your eye by watching house sparrows (so-called English sparrows) and fixing their length as a unit. They are called six inches long, and in the field other birds may be measured by them. The robin is ten inches long, and may be used to measure the larger birds.

In describing the colors of birds, great discussions often arise because pupils do not use terms correctly. Consult Chapman's "Birds of Eastern North America" for a color key or chart, and train yourself to observe colors carefully and name them correctly. You will find more colors among birds than are given there, but the chart will help you a great deal.

Study in the laboratory as many birds as you can. Try to get one of each order at least and, among the perching birds, one of each family. The answers to the following questions should be recorded upon the blank outlines of birds, or else in the form of a table.

Questions.

1. How long is the bird?

2. What is the general color of the upper surface; of the lower?

3. What are the markings or peculiarities of the head, if there are any?

4. Note any peculiarities of the tail, as to shape, length, or color, if there are any.

5. If the wings are not like the back, note their color, and, if there are wing bars, note their number and color.

6. What are the markings on the breast, if there are any?

7. Note any other markings, as rump spot, etc.

8. What sort of beak has the bird?

9. What sort of feet has it?

10. Identify the bird, using any key or guide you have. Do not ask any one to help you until you have exhausted your own resources.

Comparative Study of Birds

1. In what ways do the feet of birds vary? Give examples to illustrate your answer. What are the principal results of these variations?

2. In what ways do the beaks of birds vary? Give examples of the variations and of the special uses of the beaks.

3. How do water birds differ from land birds; flesh-eating birds from seed eaters; insect-eating birds from seed eaters; shore and swamp birds from land birds?

Work in the Field

Materials.

(1) Birds in the field, field or opera glasses, and bird guides. (2) Some extra time, as field work is rather slow. (3) Considerable energy, as birds rise early and may be up and away before the usual hour for your appearance.

Directions.

The object of this work is to become acquainted with the living bird, to learn not only its name, but also some of its ways. You will need to spend time to do this, and as a rule the more time you spend the more you will see. Every time you go out after birds, record at the time every kind of bird you see, so that at the end of the season you will know not only when each kind of bird came, but also how long it staid. When you see a new bird, record immediately its colors, markings, actions, notes, and anything else which may help you later to identify it. Do not trust to memory nor to the inspiration of the classroom. After weeks of observation, write the following summary.

Summary of the Results of Field Study of Birds

1. Over what length of time have your observations extended? Where have you studied? What have you found to be the best conditions for studying birds? How many birds have you identified?

2. When in the year do birds migrate; when in the twenty-four hours?

3. In spring migration which birds come first; which come last? What reason is there for this order?

4. What may retard migration? What may hasten it?

5. What could prevent certain birds from ever coming here, or, if they did come, from staying?

6. Name some birds which stay here permanently; some which come only for the winter; some which come for the summers; some which merely pass through, going and coming.

7. Can you see anything which may determine whether a bird will nest here or farther north? If so, what is it?

8. Why is the house sparrow so successful?

9. Why are blue jays so nomadic in winter?

10. What months do the herring gulls stay here? When do they leave? Where do they go when they leave? What do they do while they are gone? When do they return? What is their economic value?

11. How many birds' nests have you seen this spring? To what kinds of birds did they belong? If you have been able to study one in particular, give its history as far as you know it.

12. Tell what you have learned by your own observation this spring concerning the kinds of food birds eat, and their methods of obtaining food.

13. What bird songs have you learned to know? When do these birds sing most? Does a bird have more than one song?

14. What birds have you seen near your home? What attached them to the vicinity? How might you attract more birds?

Birds; Review and Library Exercise

1. What are the distinguishing characteristics of birds?

2. Give the orders of birds, with the characteristics of each order and an example of each.

3. Define and give illustrations of the meaning of the expressions: "land birds;" "water birds;" "shore birds;" "swamp birds;" "scavengers;" "policemen of the air."

4. Discuss the temperature of birds, the amount of energy they show, and the oxygen they use.

5. Beaks of birds.

6. Feet of birds.

7. The crop and gizzard. Why absent in many birds?

8. What is there in a bird's construction which enables it to twist its head so far around? What are the advantages in being able to do so?

9. Account for the oiliness of plumage of water birds; for the complete feathering of legs and feet in some forms.

10. Define moulting and discuss its advantages and disadvantages.

11. Give reasons why you would not expect a bird to hibernate.

12. Name two or more kinds of birds which show "recognition marks." What sort of birds would you expect to find with such marks? Why?

13. Is a bird's egg alive when it is laid? Why does it have so much food stored in it? What direct interest have we in this fact?

14. How are the eggs of various birds protected while they are developing?

Note.--Do not be satisfied with only one way. A bird seldom is.

15. Compare præcocial and altricial birds as to their stage of development when hatched; the location and character of the nest; the care given by the parents; the singing habit of the parents; the success of the type.

16. Name at least three insect-eating birds and tell how many insects it is estimated each will destroy in a day. Effect in a garden?

17. If you had an orchard to protect from insects would you spray it with poison, or would you police it with birds?

Note.--Consider both sides. There is much to be said on each.

If you decided that you needed more birds, how would you get them?

18. Suppose you had a city lot in the suburbs, 50 feet wide by 200 feet deep, with a house covering the first 50 feet. Make a plan of the back yard to show what you could do to attract the birds to it in the summer; in the winter. Remember that birds must have protection against enemies as well as against changes in weather, etc.

19. For what purposes are birds killed by man? Which of these do you consider legitimate? Which birds may not legally be killed at any time of the year in this state? Which may at certain seasons? Which may at any time? When should an "open season" be permitted? How long should it last?

20. Give a short biography of Audubon. Describe the purpose of the Audubon Society and some of the work accomplished by it.

21. When were the house sparrows, or, as we call them, the English sparrows, introduced into this country? Where? Why? Have they proved a success from our standpoint? From their own? Why have they increased so enormously? What part of the country is still free from them? Why? Give the reasons for and the methods of fighting English sparrows.

22. The history of the passenger pigeon.

23. What has the quail or bobwhite to do with our food supply?

24. Poultry keeping.

25. Name three bird magazines and give a characteristic of each one.

26. Fossil birds and the light they shed on the probable ancestry of birds.

Study of the Migration of Animals in General

The migration of birds is only one case of a phenomenon which is comparatively common. From your text and reference books find other examples of migration. What are the causes which make animals migrate? What methods do various animals use? What are some results of these migrations? Summarize your study in the following thesis:--

The distribution of animals.

1. The necessity for this distribution.

2. Methods of distribution--voluntary--involuntary.

Note.--See in review the methods used to spread corals, hydroids, and other sedentary forms, starfish, clams, etc., as well as those used by the various vertebrates.

3. Time when migration occurs. Consider here the young of most animals, and the movements of many birds, as well as movements caused by some accidental occurrence.

4. Distance that animals move from the place of their birth.

5. Factors which determine the routes of distribution.

6. Factors which limit distribution.

Migration maps.

1. A map to show the migration route of the birds of your region.

2. A map to show the migration of the potato beetle (or English sparrow or any other animal the extension of whose range has been studied).

3. A map of the world, showing the zonal areas.

4. A map of North America, showing the distribution of the ungulates, with the boundaries and barriers marked.

5. A map of North America, showing the distribution of the fur-bearing animals.

6. A map of the world, showing the distribution of the human races.

#E. STUDIES OF MAMMALS#

#To illustrate Man's Relation to Other Animals; the Connection between Mode of Life and Structure#

The Rabbit

The effects of domestication upon an animal. A burrowing type of rodent.

Materials.

Living rabbits--young rabbits are more desirable for laboratory study.

Observations.

The Body.

1. What divisions of the body are there? Compare the length and use of the neck with that of the pigeon. Describe the character and length of the tail. What use has it, if any?

Locomotion.

2. What methods of locomotion has the rabbit? Which is most commonly used?

3. Study the limbs, and find the ankle and wrist. Does the rabbit walk on its foot or its toes? Note the number and character of the toes and fingers and their claws. What is the effect of the nonretractile power of the claws upon the uses to which claws can be put?

4. What uses have the fore or the hind limbs other than locomotion? Explain how the usual sitting or resting posture is advantageous for quick locomotion.

5. By means of printer's or writing ink smeared over the soles of the feet, and a long piece of clean white paper get prints of a rabbit's tracks as it hops over the paper. Explain how the peculiar formation of the tracks occurs.

Feeding.

6. Offer a rabbit various kinds of food. How does it test the food before eating? Does the rabbit ever use its forelimbs to assist in feeding? If so, when and how? How is the food eaten? How are the teeth fitted for the rabbit's method of feeding? Does your rabbit drink? If so, how?

Respiration.

7. What movements of the body are concerned in breathing?

8. Compare the frequency of the breathing movements with your own. Can you distinguish the heart beats? If so, how and where? Count them.

Sense Organs.

9. Note the position of the eyes, shape of their surface, shape and size of the pupil. What external protecting structures are present,--such as eyelids, eyelashes, eyebrows? Study the movements of the eyelids. Is there a third eyelid as in the bird? Compare the use of the neck in enlarging the range of vision with that of the bird. Is the rabbit's range of vision greater or less than your own?

10. What is the location of the nostrils? What advantages are gained by the prolongation of the face forward? Note any peculiarity in the form or movement of the nostrils. How do you explain these movements? Are the nostrils more or less useful than those of other vertebrates you have studied? How?

11. Note the shape, size, and position of the external ears and explain what relation, if any, these characters of the ears have to hearing. Note the various movements of the ears and the reasons for these movements.

12. What special organs for touch has the rabbit? Under what circumstances are these of use? What parts of the body are most sensitive to touch?

Protection.

13. What home-making habits do you observe in the rabbit? What habits relating to secrecy, comfort, and safety, do you observe?

14. Study the fur and hair of the rabbit. How do you distinguish between fur and hair? What variations do you find in the fur and hair? What parts of the body are uncovered? Why? What are the various functions of the fur and hair covering of rabbit?

15. Have rabbits any means of defense or offense? Explain.

Social Habits.

16. Notice and describe anything in the behavior of the rabbits which may be classed as social,--such as play, fondness for company, display of affection, homing instincts, care of young, etc.

Supplementary Study of Wild Rabbits

If you cannot answer these questions from observations of wild rabbits, the answers may be obtained by reading some good natural history. Ernest Thompson Seton's story of a rabbit's life is good for the purpose.

1. What method of locomotion is more highly developed in wild rabbits than in domestic rabbits? Why?

2. When do wild rabbits do their feeding? Why? In what ways do they sometimes do damage in feeding?

3. What senses will probably be more alert than those of the domestic rabbit? Why?

4. Where do wild rabbits usually make their homes? Why? How do they guard against being cornered in their homes?

5. In what ways do they guard against surprise when feeding? What are the principal enemies of rabbits? What devices do they employ to escape enemies when pursued by them? What is thumping? When used?

6. How many young rabbits are usually produced at one time? How many litters in a season? How long does it take a young rabbit to mature?

7. How are the young of rabbits guarded against danger from enemies and weather? What are the various causes that tend to keep down the numbers of rabbits?

8. Give an account of the plagues of rabbits in Colorado and Australia, including the reasons for the great increase in numbers and the methods used to destroy the rabbits.

Summary of the Study of Rabbits

1. What has been the general effect of domestication upon rabbits?

2. What are the most important characters and habits that fit the wild rabbit for its life?

The Guinea Pig or White Rat

Materials.

Living animals.

Observations.

1. What regions of the body can you identify? What is the relative length of the neck, ears, legs? What about the tail?

2. Describe the color scheme of the animal. Is it protective or the result of breeding? What is the character of the covering?

3. Describe the method and rate of locomotion. Would this method of locomotion enable the animal to escape from enemies (e.g. dogs)?

4. What is the shape of the foot? What is the shape and length of the claws? For what are they adapted?

5. What sounds do the animals make?

6. What is the appearance and shape of the eye? What is the color of the eye?

7. State the size and shape of the external ear. What movements are characteristic?

8. What motions of the nostrils do you see?

9. Feed the animal various kinds of food. How does it eat? State any facts you observed, to show that it has or has not a choice as to food.

10. Watch the animal for some time to determine its mental characteristics. Is it alert? curious? timid? Does it show much intelligence? affection?

What is the relation between mental development and success in the struggle for existence?

Summary.

1. What are the general characteristics of the animal?

2. To what kind of life is it adapted?

3. What are some of the characteristics that make the animal a good pet?

The Squirrel

Materials.

Living specimens in cages, mounted specimens, pictures, charts, lantern slides, etc.

Directions.

Before taking up the study of the squirrel in the laboratory a trip should be made to some park or wooded region and the habits of squirrels noted. Take your camera and try to take some snapshots. After the laboratory exercise visit some museum or zoölogical garden and study the relatives of the squirrel.

Observations based upon field work.

1. What different postures does the squirrel assume?

2. What does it do when frightened?

3. What use have the forelegs other than locomotion?

4. How does a squirrel go up a tree? down? from branch to branch? State all the forms of locomotion you have noticed.

5. What is the appearance of the tail? What is the position of the tail when the squirrel is sitting? running? on a branch? Describe any motions of the tail you noticed. Is there anything expressed by these motions or are they without meaning?

6. Tempt the squirrel with some nuts. State the evidence that leads you to think that the squirrel is alert, timid, curious. Do you think the squirrel acts most from instinct or as the result of intelligence?

7. In what various ways does a squirrel attempt to escape notice? What does it do when you chase it?

Observations in the laboratory.

1. What divisions are there to the body? What is the length of the neck? the length and appearance of the tail?

2. What is the relative length of the legs as compared with the body? How does the length of the front and hind legs compare?

3. Does the animal walk on its toes or on the sole of its foot? How many toes on each foot? What is the length of the claws? For what could they be used?

4. Offer the squirrel various kinds of food and see if it has a choice. Describe its methods of eating.

5. Note the position of the eyes, the shape of their surface, and the shape and size of the pupil. How many eyelids do you notice? Why do the squirrel's eyes appear so "bright"? Are eyebrows, eyelashes, or tear glands present?

6. Note the size, shape, and appearance of the squirrel's external ears.

7. What movements of the nostrils do you notice? For what does a squirrel chiefly use his nostrils? What explanation can you suggest for the nostrils, eyes, and ears having the same relative position in all vertebrates?

8. How does a squirrel protect itself?

9. Smear the feet of a squirrel with ink and allow it to run over a roll of clean paper as in the case of the rabbit. How do its tracks differ from those of the rabbit?

Summary.

1. What are the general characteristics of the squirrel?

2. To what kind of life is it adapted?

3. What adaptations has the squirrel to protect it from its enemies?

4. What characteristics make the squirrel a good pet? What objections to it?

Library Exercise on Rodents

1. General characteristics and examples of rodents. The teeth of rodents.

2. Show how variation in habitat depends upon structure among rodents by comparing, for example, squirrels, beavers, and woodchucks.

3. Variations in the tails of rodents. What are the causes of this variation?

4. Pocket gophers and their economic relations.

5. Species of mice. Their habits.

6. The dancing mouse.

7. Damage by mice. Plagues of field mice in Nevada. Method of extermination.

8. Habits and kinds of rats.

9. Economic importance of rats. Methods of extermination.

10. Rats and the bubonic plague.

11. Squirrels, kinds and habits.

12. The economic value of rabbits.

13. The groundhog myth. Habits of woodchucks.

14. The beaver--their habits and sagacity. Methods of trapping them.

15. Prairie dogs--their habits and economic importance. How exterminated?

16. What are porcupines?

17. Variation in the homes among rodents. Usual means of defense.

18. Make a list of rodents in a column, and in another column opposite each name write the various ways the animal is of economic importance. Sum up with a statement showing the most important ways rodents are of value to man and harmful to man.

19. Defend the proposition that rodents are on the whole harmful animals and should be exterminated.

20. How some rodents contribute to the science of medicine, more especially to bacteriology.

The Cat or Dog--Carnivora

Materials.

Living specimens of cats or dogs. Pictures, books, lantern slides, etc. Supplement the laboratory study with trips to museums and zoölogical gardens to observe the relatives of the cat.

Definitions.

Carnivora. An order of mammals, chiefly flesh-eating, with claws and well-developed canine teeth.

Carnivorous, flesh-eating.

Herbivorous, plant-eating.

Omnivorous, eating both plants and animal food.

Digitigrade, walking on the toes.

Plantigrade, walking on the soles of the feet.

Vibrissæ, long hairs on the face--"whiskers."

Observations.

1. Into what regions is the body divided?

2. What is the shape of the head and the length of the neck?

3. Are the legs relatively long or short? How do the front and hind legs compare in length? How many toes on each foot? Is the cat digitigrade or plantigrade?

4. How many pads on the sole of the foot? What use can you suggest for these structures? What is the size and shape of the claws? Are they retractile or nonretractile? For what purposes may the claws be used?

5. Describe the tail as to length and appearance. Movements.

6. What is the size and appearance of the external ears? What movement do you notice?

7. Are the eyes large or small? What eyelids can you find? What other accessory structures? What is the shape and direction of the pupil?

8. What other sensory structures do you find? What is their function?

9. Watch the animal eat. Does it chew or "fletcherize" its food? What teeth seem well developed? Is the movement of the jaws simply up and down, or is there a lateral movement as well?

10. Try to find out some of the mental characteristics of the animal, i.e. is it sluggish or active? Is it alert? Does it show curiosity? fear? What evidence of intelligence?

Supplementary studies.

a. Smear the feet of a cat with ink and allow it to run on a sheet of clean paper. Make a diagram to show tracks. Do the same in case of a dog. How do these tracks differ? Why?

b. What is the difference between a cat and a dog as to the manner of eating a bone?

c. As you see dogs and cats outside do you see any evidence in either case of a tendency to gather in packs (gregariousness)?

d. What different emotions are expressed by a dog's tail? a cat's tail?

e. What sounds do cats and dogs make? Significance?

f. Contrast the sleeping habits of cats and dogs.

g. How large is the litter in case of dogs and cats? Condition of young at birth? How long before the eyes of the young are open? Care of young.

Summary.

To what kind of life does a cat or dog seem best adapted: (a) as to food? (b) protection from enemies?

Carnivora; Review and Library Exercise

Characteristics.

1. The general characters of carnivora.

2. Five important families. The characteristics and examples of each family.

Morphology and physiology.

3. The dentition of the cat, the dog, and the bear. Variation in the "chewing teeth."

4. Three types of paired appendages among carnivora. Relation to habitat.

5. The difference in structure and use of the posterior legs of the seal and walrus.

6. The alimentary canal of a cat and rabbit compared.

7. The tongue of cats and dogs contrasted as to structure and use.

Economics.

8. The difference between hair and fur.

9. The fur-bearing carnivora. Families, and habitat.

10. Trapping.

11. Game laws and game wardens. Hunters' licenses.

12. Hunting big game.

13. Carnivora harmful to man.

14. Carnivora useful to man.

15. Carnivora as pets.

16. Chief types or breeds of domesticated dogs. Characteristics. Special value of each.

17. Chief types or breeds of domesticated cats.

18. Dogs as burden bearers.

Natural History.

19. Distribution and range of carnivora. Carnivora of the United States.

20. Winter habits among carnivora.

21. Food of carnivora. Various methods of obtaining it.

22. The hunting habits of the dog and cat family.

23. The habits and distribution of the raccoons.

24. The color schemes of the more important families of the carnivora.

25. Seasonal variation in color.

26. Distribution and habits of the ferrets and weasels.

27. How carnivora protect themselves from enemies. Which carnivora have been most successful in resisting man's advance?

28. Peculiar and interesting carnivora to be seen in museums and zoölogical gardens.

29. Origin of the domestic dog.

30. Intelligence of dogs.

31. Fox-hunting.

32. Coyotes and their relation to stock raising, etc.

The Ungulates

Materials.

Pictures, charts, lantern slides, and books showing cow, sheep, hog, goat, horse, etc. Diagram of skeleton.

Directions.

Since it is impossible to have living ungulates in the laboratory, this study should be supplemented by trips to a museum and to a zoölogical garden. Observe also such hoofed animals as may be common in your neighborhood. Use your camera and make "snapshots," showing characteristic attitudes of these animals.

Definitions.

Ungulates, an order of mammals characterized by the possession of hoofs.

Ruminant, a division of ungulates, which "chew the cud."

Perissodactyl, a division of ungulates with an odd number of toes.

Artiodactyl, a division of ungulates with an even number of toes.

Carnivorous, flesh-eating.

Herbivorous, plant-eating.

Omnivorous, eating both plant and animal food.

Observations in the laboratory.

Note.--Answer the following questions for one or more of the following: The cow, sheep, goat, hog, and horse. If desired, the questions may be answered in the form of a table.

1. What is the relative length of the neck? What is its direction with reference to the body? Of what importance is this length and direction?

2. What is the length and appearance of the tail? What is its use?

3. What is the relative length of the legs? Locate the heel, knee, and elbow. (Reference should be made to a diagram of a skeleton.) When the leg is long, in which bone is this lengthening accomplished (compared with human skeleton)?

4. How many toes on each foot? Is the animal an artiodactyl or a perissodactyl? Is it plantigrade or digitigrade?

5. What is the relative size and position of the ears (external ear)?

6. What is the relative size and position of the eyes? nostrils?

7. Are horns of any kind present? If so, note the size, shape, and direction. Are they present in both sexes? If not, in which one? If in both, note any differences distinguishing the sexes.

Suggested drawings.

a. Head, side view.

b. Entire animal, side view.

Observations in the field or at home.

1. Note how the animal uses its lips, tongue, and teeth in feeding. Is it a ruminant?

2. In what order does the animal use its feet? Look up the definition of walk, run, gallop, canter, trot, lope, single foot, pace. Which of these forms of locomotion are optional with the animal?

3. Describe the process when the animal lies down and gets up.

4. Describe the covering of the animal, noting its length, fineness, etc. What variations in different regions of the body?

5. Is the animal alert or sluggish? Upon what senses does it most depend? What mental characteristics are most marked, e.g. curiosity, fear, suspicion.

6. Note any movements of the ear. What is gained by these movements?

7. What is the position of the eye? What is the shape and direction of the pupil? Reason?

8. What means has the animal for getting away from its enemies.

Observations based upon museum trip or natural history.

1. Identify as many ungulates as you can; for example, buffalo, musk ox, big-horn sheep, Rocky Mountain goat, chamois, antelope, giraffe, red deer, elk, moose, reindeer, wild boar, peccary, rhinoceros, zebra, hippopotamus.

2. Answer the following questions about each:--

a. What is the family, scientific name?

b. What is the size of the animal? the relative length of the hind and fore legs? the relative length of the neck?

c. What is the nature of the covering of the animal?

d. Are any horns developed? If present, what is their size, shape, direction, and appearance?

e. What is the habitat of the animal? its distribution and social life?

Summary.

In a short thesis summarize the facts you have found out about ungulates, using the following outline:--

1. Why called ungulates? Variation in number of toes.

2. General fact about the food of ungulates. The two divisions.

3. The general adaptations for protection.

4. The social life of the ungulates.

5. The native ungulates of the United States.

6. Commercial uses and value.

Ungulates: Review and Library Exercise

Characteristics.

1. Classification of ungulates based upon number of toes, kind of horns, "chewing the cud," etc. Some of the more important families with examples.

Morphology and physiology.

2. The variation in the number and kinds of teeth. The dentition (or dental formula) of horse and cow.

3. The various types of horns. Shedding of horns and sexual variation.

4. The structure and function of the stomach of a ruminant. Meaning of the cud-chewing habit.

5. The structure of the stomach of a camel.

Economics.

6. Ungulates which have been domesticated.

7. Breeds of cattle--their distinguishing marks and valuable points.

8. Breeds of horses--their distinguishing marks and valuable points.

9. Breeds of sheep--their distinguishing marks and valuable points.

10. Breeds of hogs--their distinguishing marks and valuable points.

11. Angora goats.

12. The making of butter and cheese. Kinds of cheese. Substitutes for butter.

13. The packing industry. Ungulates useful as food.

14. The various methods of preserving meat.

15. Cattle ranches and "round-ups." Free cattle in winter.

16. Cattle raising in your state; in other countries.

17. Transportation of cattle. Stock cars, care and feeding.

18. Useful products derived from ungulates.

19. Tanning. Varieties and use of leather.

20. Diagrams showing chief cuts of meats.

21. Sheep husbandry. Shearing.

22. Ungulates as beasts of burden. Advantages and disadvantages.

23. Government inspection--quarantine.

Natural History.

24. Geographical distribution of ungulates. Habitat and range.

25. Native ungulates of North America.

26. How, when, and by whom cattle and horses were introduced into America.

27. The geological history of the horse.

28. The story of the buffalo.

29. Deer hunting.

30. Methods of protection from enemies among ungulates.

31. Breeding habits and care of young in case of ungulates.

32. Intelligence in the case of horses.

33. Strange and peculiar ungulates to be seen in museums and zoölogical gardens.

The Horse

The pupil is expected to study carefully the account of Eohippus or Hyracotherium in his text or any other available reference book, and to supplement that work and this brief sketch with original observations upon horses on the street, at a local store, or wherever possible or convenient.

From the early horses which migrated from North America there arose in Asia and Africa the ass, famous in the history of early civilization and still used in some localities as beasts of burden or for the breeding of mules, which are the crosses between ass and horse. There also arose the zebra and the most primitive of modern horses, Przewalskii's horse, a wild pony of western China, about forty inches high and almost identical with the drawings of the horse made by early man, 30,000 years ago. Doubtless the modern ponies of Ireland, Iceland, and Shetland are descendants of the original Przewalskii type and not, as is often claimed, true horses stunted by rigors of climate and scant fare.

The horse is characterized largely by the presence of a lock of hair between the ears, a full mane and tail, small ears, large hoofs, and peculiar neigh. The ass has no forelock, a scanty mane and tail, long ears, small hoofs, and a distinct bray.

By means of various crusades and raids, the modern horse was introduced into Europe from Asia, where it is clearly traced in history to the reign of King Solomon. Here, in Europe, because of local conditions and demands, it assumed differing type forms. The roadster type is closest to the Arabian in character. The draft or heavy type was bred in western Europe when heavy armor came into use for rider and horse, and the coach or carriage type was developed when armor was abandoned for gunpowder. Finally explorers and colonists brought the horse back to America, its original home.

The various types and varieties may be briefly described.

A. The draft type has short legs, short neck, large round body, and ranges in weight from 1400 pounds to 2000 pounds.

Varieties:--

1. Percheron: generally about 1700 pounds in weight, 16 hands (64 inches) high, gray or black, blocky body, steep rump, clean legs, and quick action.

2. Shire: generally about 1800 pounds in weight, 17 hands high, bay or brown, white marked feet and face, hairy legs and feet, and slow action.

3. Belgian: generally about 1800 pounds in weight, 16 hands high, chestnut or roan in color, compact body, short, steep rump, and small feet.

B. The coach or carriage type has legs and neck of medium length, a body full-chested but not blocky, and a weight varying from 1150 pounds to 1400 pounds.

Varieties:--

1. Hackney: generally of full, broad, powerful body, short legs and back, high action and high carriage of neck and head, bay or chestnut in color, 15 hands high, and 1400 pounds in weight.

2. Coach: generally lighter than the Hackney, with longer legs and long stride; height, 16 hands; weight, 1300 pounds.

3. Cleveland bay: averaging 16-1/2 hands in height, 1350 pounds in weight, high, broad hips, strong action, and bay color.

C. The roadster type is long and lean of limb and body, and averages about 1100 pounds in weight.

Varieties:--

1. Thoroughbred: of small head, long neck, level back, of variable color, 14-1/2--16-1/2 hands high, about 1000 pounds in weight.

2. American saddle: an American production; not a distinct breed, but a roadster of high quality.

3. American trotter: a superior type of good speed. The off forefoot and the nigh hind foot act together, the nigh fore and the off hind feet together, giving a two-beat gait.

4. Pacer: similar to the trotter, but using both off feet and both nigh feet together, giving a swinging gait.

The horse is very similar to man in its physical and mental character, being subject to the same ailments and treatment and having the same impulses of affection, hatred, fear, jealousy, obedience, willfulness, memory, and perhaps reason. It is of all animals most careful in its eating and drinking; because its stomach is small, the food should not be bulky but concentrated, grain forming a goodly portion of the ration.

Perhaps the most important point in the structure of the horse is the form of the leg and foot. The shoulder should slope slightly backward and the pastern joint, immediately above the hoof, slightly backward. The hips, or "quarters," should slope downward somewhat, and the hock should be comparatively wide to afford ample leverage for the pulling muscles. The legs should be straight as pillars when seen from front or rear. The outer walls of the hoof support most of the weight though the frog should normally touch the ground. In nature the hoof wears away properly of itself, but the shod hoof needs regular trimming attention, while the frog must not be trimmed, for it is the soft growing part that nourishes the hoof. In this treatment the foot is comparable with the human finger and finger nail.

Observations.

If access to a living animal is impossible or inconvenient, the pupil may use reference book or pictures for most of these points. A measuring tape or ruler should be at hand, and the assistance of an experienced person is a valuable aid. If several horses are studied, they should be distinguished by name or number.

Record the color, condition, weight, and height of the horse at the shoulder. (Height is given in "hands," a hand being the breadth of the palm, or 4 inches.) Note the slope of the shoulder, of the back and the hips, the general form of the head and neck, and the facial expression. Find the chestnuts, warty growths on the inside of each leg. Examine the foot, finding the V-shaped frog in the center, surrounded by the horny hoof.

Find the pulse by passing the fingers downward from the upper curve of the neck, along the inside of the jaw; count the pulse. Notice the position and motion of the ears with their lining of hair, and the position of the eyes, the form of the pupil, and the probable range of vision. Watch the horse use its lips, and examine the mouth and teeth, finding the grinding teeth far back in the mouth, the incisors in front, and the space where the canines are missing.

The male may have canines in the upper jaw.

On the surfaces of the incisors are the depressions, or "cups," by means of which age is determined.

At six years the cups leave the lower center teeth; at seven the adjoining teeth; and at eight, the outer lower teeth. At nine years they leave the upper center incisors; at ten, the adjoining teeth; and at eleven, the outer teeth above. At the age of ten years a spot appears in the outer upper incisors, at fifteen years the groove has worn to the center of the tooth, and at twenty-one years the groove is worn to the bottom of the tooth.

Questions.

1. Describe the horse you studied as to its name or number, its color, markings, weight, and size. Of what type and breed is it a specimen?

2. Upon how much of the foot does the horse walk? How does this affect ease or speed of action? How does an athlete imitate this in sprinting?

3. How many toes has each foot? What advantage or disadvantage can you see in this unusual structure?

4. How is the hoof constructed to distribute the weight over a surface broader than the leg? How general is this among terrestrial animals?

5. What is the difference in the position of the chestnuts of the fore and hind legs?

6. Where in the foreleg is a springiness permitted by curvature? Where does the back leg accomplish the same thing?

7. How do you account for the elongating of the face?

8. Explain the uses of the lips, telling how they are fitted for their work.

9. Tell where the bit lies in the horse's mouth, and how the structure permits this.

10. Where are the ears situated? How does this peculiar position affect the range of hearing and general alertness? Of how much movement are they capable? Describe the lining of the ear, and state its use.

11. What is the rate of the pulse?

12. Measure the height at shoulder and at croup, length of body from withers to rump, of head, of neck; thickness of body from the shoulder to the chest and of distance of chest from ground. Point out any equalities or ratios you find.

Topics for investigation.

1. The meaning of the terms gee, haw, nigh, off, run, gallop, trot, pace, single foot, rack.

2. The location, cause, and effect of these troubles: heaves, blind staggers, knee sprung, shoe boil, quitter, ring bone, spavin, capped hock, flat foot, hoof bound, glanders, mange, sweeny, hide bound, and thrush.

3. The record time for a trotted and a paced mile.

4. The meaning of "one horse power." How much a horse can pull on good roads.

5. Record prices for valuable horses.

6. Current prices for horses; for ponies; for mules.

7. The origin and the use of the mule.

8. Balanced rations.

9. The number and care of the young, and their relative development at birth.

10. Other animals used as beasts of burden in peculiar conditions or localities.

Homology of the Vertebrate Skeleton

Materials.

Prepared skeletons of an amphibian, a reptile, a bird, another mammal, and man. If any of these be lacking, lantern-slide illustrations may be used in a partially darkened room.

Observations.

Having studied the frog's skeleton in detail, the student can readily compare each of these types with it. Compare in a very general way the skulls, the girdles, and the limbs; their form and use. Note variations in the form and number of the vertebræ and the number of the ribs.

Questions.

1. In which types of vertebrates are the joints between the skull bones bound with cartilage? How does the joining change in later types?

2. What dissimilarities occur in the series as regards closure or boxing in of the eye orbits, nostrils, and skull bones? How would these changes in joining and closure affect strength, rigidity, and protection?

3. What evidence is there that such improvement has affected brain capacity and intelligence?

4. State how the attachment of the skull to the vertebral column changes as the animal man assumes an erect position.

5. Are the vertebræ of these types alike in structure? What is the general form of an horizontally placed vertebra, as in the horse or a reptile, and of a vertically placed one, as in man? If you see any differences, account for them.

6. Wherever possible, find the vertebræ of the neck (cervical), and note the number of them in each case.

7. How is flexibility of the column accomplished in certain types or in certain places of one type? How is rigidity gained? State instances in each answer.

8. Examining the interior of the turtle's "shell," find out and explain how the vertebræ have been modified to form the upper "shell." How has the under portion (plastron) been formed?

9. In round numbers, which skeleton has the greatest number of vertebræ and which the least?

10. Which skeleton has the greatest number of ribs, and which has the least?

11. In a summarizing statement explain any variations you find in the pectoral and pelvic girdle for strength (rigidity); flexibility. This answer may be written as a table, naming the bones, opposite each stating its condition, and then what it affords or is adapted to.

12. What is accomplished by having two bones in the shank of the leg? In what types or forms is there but one, and which one is it?

13. Can you assign any advantages in power, agility, length of leg, or position of leg and foot accruing from a long ankle? (See horse, frog, et al.)

14. Enumerate the types or forms, and opposite each state the number of fingers and toes.

15. Make a table, heading one column "Form or type"; another, "Habitat"; and a third, "Habit." Judging from the structure which you see or from your previous knowledge or experience, fill in the table, stating whether the type is aquatic, terrestrial, or aërial; whether it burrows, walks, runs, or climbs, etc.

16. From your statements in 15, explain how the peculiar mode of life affects the structure of these types.