Part 98

IV. Bleaching. The bleaching fluid used is hydrogen peroxid to which ammonia is added until a white precipitate forms. The proportion is approximately two parts of peroxid and one of ammonia. The material is bleached until all the color is removed and the tissue looks perfectly clear or slightly opaque. It may be quite transparent as the protein coagulate is somewhat white, but all yellow or reddish color should be bleached away.

V. Washing. Rinse thoroughly in running tap water or through several changes of water until the odor of ammonia is quite gone.

VI. Dehydration. Pass gradually through alcohol solutions, 30 per cent., 50 per cent., 60 per cent., 70 per cent., 80 per cent., 95 per cent., and last through absolute alcohol. The time required for dehydration will vary with the size of the material, but in either 95 per cent. solution or in absolute alcohol the tissue should remain until well hardened, twenty-four hours or more. Dehydration is completed by passing from absolute alcohol, to a fluid one-half absolute alcohol and one-half benzol; thence for a few days to pure benzol.

VII. Clarifying. From benzol the material is finally clarified in winter-green oil or any other standard clearer, and put up in its final position in the museum jar.

In commenting on this method Dr. A. F. Contant says: “I have found this to work very successfully in the injection of the lymphatics of the human skin, which, as you know, is a rather delicate injection and has been difficult of demonstration by other methods. With this method, however, I have prepared whole portions, as the side of the face, the leg, etc., of small animals and embryos which show clearly the whole course of the lymphatic vessels and nodes, in situ, and their relations to surrounding parts.”

EQUIPMENT FOR THE DISSECTION LABORATORY

Figure 84 illustrates some essential equipment for the dissection laboratory. The equipment should consist of a pump, No. 1, which forces air through the rubber tube, No. 2, into the pressure tank, No. 4, which is guarded by the valve at No. 3. A dial, No. 5, indicates the pressure of the air within the tank. The air as needed is released through an outlet valve. The air now passes through the rubber tube, No. 6, into the left arm of the manometer at No. 7. The manometer is simply a glass tubing filled with mercury to the point indicated at No. 7. By the side of the opposite arm there is made a scale graduated in centimeters. The tube at No. 9 being attached to the Y-tube, conveys air under the same pressure into the injection chamber as that supporting the column of mercury of the manometer. It is necessary to have a pinch cock, as indicated at No. 11, to control the liquid within the tube. No. 12 illustrates the tube in the end of which, No. 13, there is inserted a trocar which is introduced into the artery and tightly tied with a cord.

FIG. 84.—Photograph showing injection apparatus, dissection instruments, dissection pan and death chamber.

1, Pump. 2, Rubber tube leading from pump to compression chamber. 3, Stop cock. 4, Compression air tank. 5, Pressure indicator. 6, Rubber tube leading from pressure tank to manometer. 7, Top of mercury in manometer tube. 8, Open end of glass tube showing scale in centimeters. 9, Tube leading from 4 to injection chamber. 10, Injection chamber containing injection fluid. 11, Pinch cock on rubber tube connecting injection chamber with injection canula. 12, The tube. 13, Injection canula. 14, A metal dissection tray. 15, Death chamber. 16, Base of same. 17, Rubber tube connecting gas cock with death chamber. 18, Bone saw. 19, Bone cutter. 20, Scapula. 21, Tenaculum. 22, Forceps. 23, Straight scissors. 24, Small pair of curved scissors. ]

A convenient dissection tray may be made from galvanized iron. It should be 16 inches square and about 1 inch deep (Fig. 84, No. 14).

A death chamber is made by using a bell jar 12 inches in diameter at the bottom. This is used on a perfectly smooth board 16 inches square. Through the center of this board is inserted a glass tube ⅜ inch in diameter. To this glass tube is attached a rubber tube the other end of which is attached to a gas jet.

The instruments needed in dissecting are illustrated in Fig. 84. No. 18 is a bone saw; No. 20 is a scalpel; No. 21 is a tenaculum; No. 22 is a pair of forceps; No. 23 is a pair of straight scissors; and No. 24 is a small pair of curved scissors.

BIBLIOGRAPHY

BAUM AND ELLENBERGER, Handbuch der Vergleichenden Anatomie, Berlin, 1912.

BARROWS, H. R., Me. E. S. Bull. 232, pp. 16, plates 6, 1914.

BRADLEY, O. CHARNOCK, The Structure of the Fowl, pp. 146, illustrations 73.

CHAVEAU, A., Comparative Anatomy of Domestic Animals, New York, 1893.

CURTIS, M. R., Ligaments of the Oviduct of the Fowl, Me. E. S. Bull. 206, 1910.

DUVAL, ——, Atlas of Embryology.

FOSTER AND BALFOUR, Elements of Embryology.

GADOW, H., AND SELENKA, E., Vögel. I. Anatomischer Theil (Dr. H. G. Bronn’s Klassen und Ordnungen des Thier-Reichs. Sechester Band, Vierte Ahtheiburg), Leipsig, 1891.

GRAY, HENRY, Anatomy Descriptive and Surgical, New York, 1908.

HEISLER, J. C., Embryology, Philadelphia, 1901.

KAUPP, B. F., Male Reproductive Organs of the Fowl, Am. Jr. Vet. Med., vol. x, 11, 2.

KAUPP, B. F., Female Reproductive Organs of the Fowl, Am. Vet. Rev., vol. 49, 11, 4.

Leisering Atlas of Anatomy, edited by W. ELLENBERGER, translated by A. T. PETERS, Chicago, 1905.

LILLIE, F. R., Embryology of the Chick, Chicago, 1906.

OWEN, R., Comparative Anatomy and Physiology of Vertebrates, London, 1866.