SECTION V. Diseases of the Lymphatic Tissues Including Spleen

DISEASES OF THE LYMPHATIC TISSUES INCLUDING SPLEEN

Since we have followed diseases of the blood from the simple anemias to a place where mononucleosis in the circulatory system and in the fixed tissues is the prominent feature, another step reaches the area whence most of these cells emanate—the lymphatic system. The anatomical and physiological position of the lymphatic circulatory apparatus is closely analogous in the classes under discussion, and it stands in an anatomico-clinical sense, closer to the hematopoietic system than to any other structures, throughout the whole animal creation. This anatomical division of the circulation is closely comparable, for pathological purposes, in the mammals whereas in the birds one finds noteworthy variations. In the class Aves lymphatic radicals are extremely numerous, the plexuses in the extremities and thorax perhaps being complemental for the rather scantily supplied blood vessels. About the fibulo-tibial and femoral muscles the tiny lymph vessels form an extraordinarily dense and intricate lacework, a replica of which may be found in muscles of the upper limb, while in the pelvis and thorax a rich plexus is distributed around both kinds of blood vessels and also lies within the walls of air sacs. The air sac walls in the chest display lymphatic lines very well in birds that have been for many years exposed to railway dust, the natural pearl gray glistening membrane looking as if black pepper had been evenly dusted over it. The lymph glands or compound nodes so easily discovered in mammals are practically absent in birds. Along the large thoracic vessels and in the pelvis of some anserine and struthious varieties, small illy defined masses of lymphatic tissue may be discovered by careful search but they do not possess nodal arrangement and capsule. Lymph follicles on the other hand, are quite numerous in the respiratory, and especially, the intestinal tract. Groups of follicles may also be found in the lining of the upper ends of these tracts in such situations that the names faucial, pharyngeal, or even tubal tonsils are justly applied. I do not find any reference to a lingual tonsil in birds, but this structure is found, with of course many modifications, down as far as the monotremes. The lymphoid tissue of the nasopharyngeal region is so placed in animals as to be exposed to aerial and food infections, just as it is in man. It is, however, noteworthy that chronic inflammations leading to hypertrophy or to obstruction have not come to our attention. There is only one diagnosis of chronic tonsilitis in our records, a determination based upon the nodular red-brown prominence of the tonsillar region, but there were no true hypertrophy and areas of fibrosis combined with necroses as seen in human medicine; this case concerned a Chacma baboon.

HYPERPLASIA.

In so far as the reaction to infectious or toxic agents is concerned there seems to be a fairly uniform character through the mammalian groups, but in the Aves there are a few differences worthy of mention. It is at once admitted that these observations upon birds are based upon a very few sections of isolated lymphatic tissue, but they are supported by records of the changes in nodes in mucous membranes and viscera, and by those in the spleen. The first and perhaps most noteworthy difference is in the paucity in birds of large mononuclears of the endothelial type. Their position in chords, sinuses and germinal centres is taken by deeply staining mononuclears, of the size and general character of large lymphocytes as seen in the blood. The hyperplasia in the follicles is much more dense but it is outdone by that in the chords. Since the nodal tissue of birds is not so sharply delimited by some sort of capsule, it is but natural that the hyperplasia should be diffuse; in the intestinal wall it may extend laterally twice or thrice the width of the normal follicle. Necrosis, unless the disease be mycotic, tuberculous or parasitic, is uncommon.

It may be well to discuss for a space the reaction to infection of the thoracic and intestinal lymphatics in mammals. The amount of lymphadenoid tissue in the mediastinum is very great in some mammals, notably the Ungulates, while in others, the Rodents and Primates, for example, it is not so plentiful. Nevertheless the gross and minute changes are usually of the edemato-exudative type—large, pink, soft, moist glands. In the abdomen, on the other hand, one usually finds well outlined, firm, yellow nodes in the mesentery and behind the peritoneum. This is not only to be discovered in various chronic diseases of the intestine but even in acute, so-called toxic enteritis seen in carnivores from food poisonings. One must therefore ask if the local nodes abundant in the intestinal mucosa do not take up the poisons which cause the acute hyperplasia and are in turn backed up by the stalk glands. Even in so acute and overwhelming a disease of the intestine as hog cholera (which we have not had here) the glands retain their general structure, although hemorrhagic, while in late stages they become firm, sharply outlined and pigmented. In birds there may be swelling of the omental bursæ, but as there are no lymph glands no masses are found.

The response on the part of the lymphatic tissues as a system, or some large section of this system, is shown in the following figures. It is our practice to include in the diagnosis general acute or chronic lymphadenitis or inflammation of a large drainage area. Acute changes have been mentioned 103 times, in which the important orders are represented as follows: Primates 21, Carnivora 46, Ungulata 15, Rodentia 3, Marsupialia 13, Pinnepedia 4. Chronic changes are mentioned 43 times as follows: Primates 7, Carnivora 19, Ungulata 14, Marsupialia 1, and Pinnepedia 2. This great proportion among the Carnivora does not indicate that they have more lymphatic structures for such an advantage is probably possessed by the Ungulata, but perhaps should be interpreted as an evidence for this order of the ready response to irritation on the part of the tissues in question. They probably suffer more, as we shall see later, with inflammation affecting drainage tracts. The hyperplasias or inflammations included in the figures above most often accompany gastroenteritis, pulmonary diseases or long standing infectious processes such as arthritis, while there are also lymphatic enlargements both local and general, associated with skeletal degenerations (rachitis-osteomalacia) and with thyroid disease. The former may be described as lymphadenitis, the latter as lymphatic hyperplasia.

Unlike lymphadenitis, a condition associated with some definite infectious or toxic cause, systemic hyperplasia of the lymphatic tissue may be apparently primary and causeless. In a pathological and clinical sense alike these hyperplasias are protean in their manifestation, making a satisfactory classification extremely difficult. For our purposes they are divisible into acute and chronic, associated with an increased number of circulating lymphocytes and without such a lymphocytosis.

The first, acute systemic lymphatic hyperplasia, is known in man as status thymicolymphaticus, a well recognized condition chiefly encountered in youthful males having some of the stigmata of the opposite sex. There is no record, nor have I any recollection of a pathological state in a wild animal comparable to this condition.

If acute generalized lymph node increase be associated with lymphocytosis, acute lymphatic leucemia exists; there is no case in our records. Chronic enlargement of lymph nodes with increase of circulating mononuclears is chronic lymphatic leucemia; a case of this has been cited under leucemia.

LYMPHOMATOSIS.

Chronic enlargements of the lymphatic tissues without leucemic blood present a bewildering number of varieties, the best known names of which are Hodgkin’s disease, aleucemic leucemia, pseudoleucemia and lymphomatosis. On occasion they are at first localized tumors, being generalized only late in the course; under these circumstances they are usually classed with neoplasms in the form of leucosarcoma and lymphosarcoma. Examples of lymphatic disease answering the above description are limited to two, but even these must be explained in certain particulars. There has already been quoted under leucemia a case of a common Marmoset (Callithrix jacchus) which was probably aleucemic leucemia of the myeloid variety; the enlargement of lymphatic nodes was trifling. The case to be cited answers in most respects to the descriptions of systemic lymphomatosis, but there were found two conditions, enteritis and parasitism, which might be responsible for sufficient general toxemia to stimulate lymph nodes and follicles to a state of active growth. Even accepting these two cases as examples of this group, it is very plain that chronic systemic primary lymphatic hyperplasia is an exceedingly rare entity in wild animals. There has been no case resembling Hodgkin’s disease of man.

California Hair Seal (Zalophus californianus). Young ♂ four months old. Appeared to be in good health, no loss of flesh or activity.

DIAGNOSIS.—Lymphomatosis. Fatty degeneration of kidneys. Emphysema. Chronic follicular and catarrhal enteritis. Nematodes in intestines.

External appearance good. Both lungs distended and are tense; it seems almost like a spastic dilatation—a simple emphysema—beneath pleural surface are many minute petechiæ. Lung mottled red and gray. This color is present on section. Lobules clearly outlined and separable with fingers. Bronchi and vessels widely open, the latter containing small amount of fluid blood. Lymph nodes—Mediastinal, tracheal and those visible in neck are variously but definitely enlarged, firm, irregular and roughly nodular, both in appearance and to touch. On section they are red and gray, follicular border not preserved and merging with medulla; connective tissue visible; gray juice expressed. Pericardium normal. Epicardium, glistening, transparent and pale. Heart position, size and interior normal. Abdomen contained no adhesions or fluid. Pale brown-red, firm liver with smooth surface and sharp edges; markings not clear; section surface smooth; watery blood expressed from section. Gall-bladder normal, contents limpid, brown. Common bile duct patulous. Somewhat enlarged spleen, soft, yet resilient; capsule smooth; section surface pulp homogeneous brown- purple; follicles gray, slightly enlarged, clear, sharply outlined; trabeculæ faintly visible, more prominent where they are near follicles. Kidney normal in size, shape and location, with smooth, pale brown surface; capsule smooth, strips easily, section surface glistening, consistency soft yet resilient; thickness of cortex slightly wide, of medulla normal; individual lobules clear yet no increase of connective tissue between; pyramids quite pale; top of medulla a little darker; cortices, pale, striæ quite faint and seem irregular; glomeruli not visible. R. Adrenal—In upper pole are two cysts about 1.5 and .8 cm. across; no scar at this point. L. Adrenal— Wide pale purple, regular homogeneous cortex under very dense capsule; medulla reddish brown, homogeneous, quite bloody. In left adrenal is a pale gray, fairly well outlined area between medulla and cortex at upper pole about 3 mm. across.

Stomach.—Contains glass and stones; mucosa, soft, smooth, flat, yellow and pink, translucent rugæ; cardia about normal; pylorus, valve prominent but probably not hypertrophied. Duodenum—Beginning at pylorus and extending through to ileum where follicles commence, intestine contains small amount white, creamy material, serosa negative, mucosa smooth flat, pale pink, translucent. There are small nematodes, probably uncinaria, some of which are attached quite firmly. Here and there throughout the gut are bits of thickened mucosa or submucosa, 2–5 mm. across. Some of these have a tiny opening from which clear fluid can be expressed. Ileum shows smooth flat translucent mucous membrane; empty; individual follicles faint but discernible. Colon reddened mucous membrane, nematodes and little mucus. Pancreas, soft, normal in size and position, color pink gray. The lymphatics of peritoneal cavity are all enlarged; most of retroperitoneal are also. Regional lymph glands are also enlarged. The description given for mediastinal answers here. The glands of mesenteric stalk present chain of sausage-like masses. Glands in mesentery are but slightly affected. Glands within and without peritoneum at kidney are especially enlarged. Large gland behind stomach and pancreas and in front of upper end of spleen is much enlarged, thick and roughly circular; it shows much fibrosis. The regional glands are distinctly enlarged but proportionately not so much as the internal ones. Smear of juice expressed from peritoneal glands shows large and small lymph cells in about proper proportions. There are a few plasma cells. No granular cells.

Smear from bone marrow shows enormous number of premyelocytes and mast cells. Polynuclears in their early stages are not numerous. Small groups of lymphocytes, lightly packed together, noted here and there. Blood smears unsatisfactory.

Microscopical.—Lung shows distended vesicles with considerable congestion of septa and in some places red blood cells in alveoli.

Kidney.—Glomeruli contracted, relatively anemic; capsule negative; epithelium throughout in state of granular degeneration probably fatty; connective tissue not increased.

Intestines.—Show slight hyaline change in muscle fibres and nodular degeneration and disappearance of protoplasm, leaving bare nuclei and outline of the cells; submucosa loose; mucosa shows infiltration of round and plasma cells, diapedesis, degeneration and desquamation of epithelium. Section of ileum shows a hyperplasia of lymph follicles with active centre in which large endothelial cells predominate. Small swellings in submucosa consist of chronic granulation tissue, but there is no foreign body and no evidence of preëxistence of a lymph follicle.

Lymph nodes loosely arranged but in places solidly small lymphoid; chords and sinuses contain chiefly small lymph cells in which are some mast and plasma cells; follicles small and loose, and centres contain chiefly large lymph and plasma cells; connective tissue not increased yet there are some fibroblasts in follicles.

Spleen.—Shows almost entirely hemorrhagic pulp; blood destruction not active; follicles large and made up of about equal mixture of small lymph, plasma and large lymph cells; connective tissue prominent probably because of excess of blood around it.

LOCAL HYPERPLASIAS.

In this group and touching the purely hyperplastic, come the hypertrophies of the lymphadenoid tissue of the nasopharynx; this can be disposed of by stating that no true chronic hypertrophies have been seen. With most cases of gastroenteritis in ungulates, and many in carnivores, there is a swelling and redness of the tonsillar region but an exudative or necrotizing process does not occur.

THYMUS.

The thymus is rarely visible in our specimens but when found has usually been normal. An increase in size and a decrease of consistency of this organ is noted in marasmus (inanition) from failure of care of the young by the parent, but so far as can be determined this has not been adequate to cause tracheal compression. In a few cases of rachitis in the canines, the organ is large and pale along with the rest of the lymphatic system. In one of the tumors of the mediastinum to be discussed, the suspicion arose that the growth originated in the thymus; adenomata and sarcomata have been described in the lower animals.

TUBERCULOSIS.

Tuberculosis of the superficial lymph glands is rare as an independent lesion in the lower animals. Dr. C. Y. White was fortunate in seeing a monkey with a chain of fibrocaseous nodes in the cervical region, upon which before death he offered the suggestion that it was of tuberculous nature. In Primates almost all drainage glands exhibit some miliary or caseous process. One monkey rejected upon the tuberculin test had what was apparently a primary lesion in the glands at the tracheal bifurcation. In the Ungulata, lymphatic tuberculosis assumes two forms, the caseous and the cellular. The former is generally understood while the latter is more uncommon. It is occasionally seen in the “fungous tubercle” of cows, but we have seen it in deer and in another order, Carnivora. In the latter, tuberculosis being uncommon, examples in the lymph nodes were noted but twice, once caseous and once solid; this latter was made up of firm, homogeneous yellow pink masses of glands in the mediastinum, showing under the microscope solidly packed epithelioid and giant cells.

Lymphatic tuberculosis in the birds is rare; only one case is recalled (unfortunately record cannot be found) as small yellow, discrete firm nodules in the mediastinum and neck. The minute picture was of a solid arrangement of large vacuolated mono- and polynucleated cells which were so packed with bacilli that the preparation could not be decolorized.

TUMORS.

The neoplastic enlargements are represented by a lymphosarcoma of the mediastinum in a Dorcas Goat; there were secondary growths in the liver, the kidney and several isolated lymph glands. Secondary growths from original tumors not in the lymphatic system are curiously rare, certainly much less frequent than is found in the human being. In ninety-two tumors which are known to give metastases, only three involved the lymphatic glands and only one of these could be considered as involving nodes not in the ordinary drainage pathway.

THE SPLEEN.

The spleen is an organ whose exact position in the scheme of things remains mystifying through the whole series of animals. Its functions have been arrived at largely by exclusion, somewhat by conjecture and speculation, while the acceptably proven duties are indeed few. Although this is not the place to enter into a discussion of all the points at issue concerning the anatomy and function of the organ, a few facts might be mentioned of comparative and perhaps pathological value. While the spleen has been looked upon always as the origin of blood cells in the embryo, cases in man are on record where no spleen was discovered, a condition suggesting that its absence is not incompatible with life; that such is the case is obvious for experimental or therapeutic removal of the organ is well known.

It was suggested by Virchow that at times the spleen assumes the duty of the bone marrow and the swelling of the viscus in certain anemias seems to support this statement. However, there is no physical relationship between the size of the animal and that of the spleen, nor between the available quantity of bone marrow, the obvious richness of circulating blood and amount of lymphatic tissue. This is well shown in the water mammals which have a great deal of blood in vessels and viscera yet their spleen is relatively smaller than birds of somewhat comparable size (the ostrich, for example). The Carnivora and Rodentia among the mammals, have quite large spleens proportionately, while comparable birds, Accipitres and Striges, have relatively small ones, and an absolutely small amount of marrow.

Another anomalous example of the function of this tissue is found in the hematopoiesis of birds. While there seems to be some evidence that in the spleen and liver red blood cells may be formed, there is perhaps at most times sufficient bone marrow to keep the blood cells at a proper number. There is no inverse relation between the amount of bone marrow and that of splenic bulk; that is in diving birds with their hollow bones the latter is no greater than in gallinaceous birds which have abundant marrow in all the skeleton.

It has been suggested that the spleen supplies an activator for pancreatic ferments. This receives a sort of support from the greater size of the organ in carnivores and smaller relative size in ungulates, since in the former concentrations of digestive enzymes are more often needed. Because of the greater excretion of iron in splenectomized animals or those being starved, Fischer has thought that the spleen has some power to metabolize this element; this receives some support from the statements concerning the size of this organ in the carnivorous orders. From experimental studies it appears that some relation exists between the lymphocytes and resistance to implanted tumors. If one apply this idea to the amount of lymphatic tissue and the incidence of spontaneous new growths, it is found that no definite relationship is discoverable either in terms of size of spleen or richness in lymphatic nodes. Carnivores, rodents and marsupials show a high tumor incidence and have a good lymphatic supply. Aves, on the other hand, with a poor nodal apparatus and a variable splenic bulk, show many fewer tumors than do the mammals. The mononuclears of avian blood rise normally as high as 60 per cent., of which 40–45 per cent. are of the small size.

The size of the spleen is subject to great variation not only within orders but actually within genera; it even seems that one sometimes sees two or three members of a species kept in the same enclosure, maybe with the same disease, maybe without any obvious disease, yet with definite variation in the size of the organ. This irregularity is recognized by veterinarians (Hutyra and Marek) who ascribe it to some unknown disease, past or present, and to normal variation. The lack of uniformity is seen more clearly in birds than mammals. In the former it might be due at times to low grade or inactive parasitism or, conjecturally, to toxins from incorrect diet; we shall see later that infection and intoxication seem to have a different effect. Some writers have mentioned the possibility of an idiopathic splenomegaly (?), a condition associated in youthful human beings, with anemia and lymphadenopathy, and occasionally going over into a sort of leucemia. The existence of such a condition is difficult to admit or deny; we have met nothing which could not be aligned in some fairly well defined group. Birds have a relatively larger spleen than mammals and in addition the organ seems to respond more actively in infections or intoxications, since it may reach, under active stimulation, a size ten times that of the normal organ.

ENLARGEMENTS OF SPLEEN.

Acute enlargements of the spleen, be they of congestive or “inflammatory” nature are quite common among the lower animals, a fact that is recognized in veterinary medicine. Congestions of the spleen are most often seen during acute infections and diseases of the heart and liver. The diagnosis has been made among mammals proportionately more than in birds, 27 or 1.5 per cent. to 35 to 1 per cent.

REASON FOR CONGESTIVE ENLARGEMENTS.

Perhaps this is partly due to the circulatory anatomy since in the former the arterial and venous supply is usually by one large vessel of each kind, whereas in birds the splenic branch of the cœliac axis breaks up into several small arteries and the venous return is accomplished by numerous venules some of which reënter the posterior cava almost directly, others joining with the mesenteric to form the portal; by this arrangement a more elastic system is assured. The same condition is found when analyzing the records of chronic passive congestion; in eighteen recorded cases, fourteen were mammals and four birds. In these cases the principal associated pathological lesions were pleural and pulmonary in seven, cardiac in three, renal in three and hepatic in four. While the anatomy of the splenic blood supply may help to explain the small number of congestions in Aves, it will not answer for the inflammations which occur in large numbers in this class; this will be discussed in the following pages.

Hemorrhage and infarction of the spleen are not very common, there being eleven of the former and ten of the latter and all occurring with the same indication or history of infectious disease; in one case, an opossum (Didelphys virginiana) an injury probably caused a massive hemorrhage shaped like an infarct. It is, however, curious that of the twenty-one cases only five occurred in birds, of which only one hemorrhage was in the shape to which the term infarction is best applied. There have been, as one might expect, a few cases of infected infarction, with abscess. It is perhaps worth noting that no case of hemorrhagic cyst or inspissated coagulum has been seen. Only one case of rupture is recorded secondary to acute splenitis during an acute septicemia.

INFLAMMATIONS.

It has been the practice at this laboratory to classify splenitis in three ways, (1) acute diffuse splenitis—general congestion with perhaps small hemorrhages, swelling but retention of general architecture and with no undue prominence of the follicles; (2) follicular hyperplasia— where this is the prominent gross and minute finding, the pulp being less pronouncedly involved; (3) acute splenic tumor—where the organ is greatly enlarged but with loss of the usual markings. Perhaps this separation is not warranted upon a strict etiological basis, and yet as we shall see it holds true fairly well in the toxic and infectious lesions. Moreover, from the following list it is evident how the various orders call upon the splenic tissue in disease.

TABLE 7. This Shows the Percentage of Various Forms of Splenitis in the Animals Coming to Autopsy. ═════════════════╤═════════════════╤═════════════════╤═════════════════ │ Acute Diffuse │ Follicular │ Acute Splenic │ Splenitis. Per │ Splenitis. Per │Tumor. Per cent. │ cent. │ cent. │ ─────────────────┼─────────────────┼─────────────────┼───────────────── Carnivora │ 7.│ 3.│ 1.3 Primates │ 2.5│ 4.9│ 2. Ungulata │ 2.4│ .3│ 1.2 Rodentia │ 2.6│ 4.7│ 1. Marsupialia │ 9.2│ 3.│ 3.7 Pinnipedia │ 33.│ │ Proboscidea. │ 33.│ │ Edentata │ 12.5│ │ 6.2 │ │ │ Passeres │ 3.│ 3.│ 3.8 Psittaci │ 6.5│ 2.3│ 4.1 Anseres │ 5.2│ 7.2│ 5.2 Herodiones │ 1.│ 6.│ 2. Galli │ 2.6│ 1.5│ 4.7 Struthiones │ 10.│ 10.│ 1. Accipitres │ 7.5│ 3.7│ 1.6 Gaviæ │ │ │ 5. Picariæ │ 4.│ │ 1.3 Striges │ 6.8│ 3.4│ Fulicariæ │ 3.│ 6.│ Steganopodes │ │ 10.│ Columbæ │ .7│ .7│ ─────────────────┴─────────────────┴─────────────────┴───────────────── For the meaning of italics see foot note Table 1.

The points to draw from this chart are first the greater variety of lesions seen in the birds, which apparently make greater use of the organ in defence, and the preponderance of acute diffuse hyperplasias in mammals. It is noteworthy that the Primates and Marsupialia show more of the acute hypertrophy of the spleen going under the name of tumor. It would be interesting and valuable to be able to discover exactly what determines and constitutes the conditions usually termed hyperplasia and inflammation of the spleen and an attempt was made in this direction by tabulating the data from Table 7 in terms of each diagnosis, classifying these latter also as infectious and toxic. The results of this effort are not conclusive, and while they permit of some discussion of the lesions, do not allow finished conclusions. The figures obtained by study are not illuminating. One can state, however, that in infections, either specific or not specific, more elements of the spleen were engaged in the process than when the condition did not resemble a communicable disease, but might be called toxic. Under the former condition the diagnosis of splenitis or acute tumor predominated, while under the latter follicular hyperplasia is more often recorded. Anatomical alterations in these two groups are described in the definition given in a previous paragraph and deserve no special discussion except in so far as they concern the changes in the avian splenic tumor when under magnification.

Microscopically there is a total loss of the relations in the acute splenic tumor of birds, the chords and follicles being replaced by a rather regularly arranged mass of small and large mononuclears, granular cells of the circulating types and red blood cells; pigment always seems increased. Endothelial cells do not take part in the general mass of the organ but along lymph and blood vessels their bulk and number are increased so that if the packing be not too dense one may find double lines of these cells passing through the hyperplastic tissue. There is, however, a group of seven cases (six birds) to which the term endothelial hyperplasia in the spleen has been applied. All of them show an unusual prominence of the vascular linings and of the follicular centres and perivascular areas; besides this there is a moderate general hyperplasia. An examination of the history and autopsy results in the birds indicated that they had all suffered with some rather protracted intoxication and showed a moderate anemia (four of the spleens were well pigmented).

The more chronic changes of this organ, be they moderate or of a grade to which one must apply the term fibrosis, are rather uncommon when one considers the number of animals with prolonged infection, anemia, skeletal diseases and hepatic cirrhoses; these are the conditions that take a prominent place in the associated pathology and history. There is no essential difference in the organ throughout the animal kingdom, and one may find as far down as the struthious birds analogies to the processes of domestic and human animals.

SPECIAL SUBJECTS—AMYLOID.

Amyloid changes in the spleen have occurred in the following orders: Primates, Carnivora, Rodentia, Marsupialia, Passeres, Galli, Gaviæ, and Anseres, fourteen cases in all. This infiltration is usually ascribed to long continued suppuration or chronic infection, every one admitting, however, that once in a great while a case is seen wherein no cause can be discovered. In this laboratory we have a high percentage of cases without adequate accompanying pathology so that we have called six of the above cases primary or idiopathic. The gross appearance of the spleen is in all these cases that of an enlarged, firm, homogeneous body without the sago spots usually described for this change. Microscopically the infiltration occurs first in the vessel walls, thence spreading to the sinus walls and reticulum. Joest in discussing this infiltration, states that it is comparatively rare among the domestic animals, where it may appear under the usual conditions or as a primary affection; it seems at times to follow unsuitable feeding. According to this author, the “sago” type is more common than the “bacony;” this has not been our experience. The most conspicuous example is given here.

European Badger (Meles meles) Adult ♀ . Gradual failure for two weeks.

DIAGNOSIS.—Amyloidosis. Chronic parenchymatous nephritis. Emphysema of lungs.

Muscles atrophic; fat scanty. Heart is dilated and muscle is red- brown. Aorta is jaundiced and there is a small patch of atheroma near the anterior leaflet of aortic valve and about 5 mm. above it. Abdomen contains a slight amount of clear fluid, no adhesions. Liver is normal in size, smooth surface, sharp edges, firm consistency, yellow color. The section surface is glistening, smooth and moist. The spleen is very hard, greatly enlarged (25 × 6 × 2 cm.) and lies across the abdomen over the intestines. It is pale red and very bacony. In iodin the tissue stains a mahogany brown. The kidney is normal in size. (5½ x 3 cm.). The capsule is smooth and strips easily leaving a smooth, yellow surface. Organ is firm. The section surface is glistening, has a relatively narrowed cortex and relatively wide medulla. The glomeruli are barely visible but stain a mahogany brown in iodin. The adrenals are 12 × 10 × 4 mm. The cortex is wide, dull yellow and regular. The zone beneath fades into the cortex although rather abruptly. The centre of both glands is occupied by an irregular pale yellow, sharply outlined nodule suggestive of solid medulla, tubercle or tumor. The zone between cortex and this is gray, irregular and firm. This is practically a normal figuration. The stomach is empty, mucosa apparently normal. Intestines were not opened but serosa seems normal; when opened after Kaiserling fixation they seem normal. The pancreas is normal in size, firm and pale. Lymphatics of the mesentery are slightly enlarged, soft, homogeneous pale yellow.

HISTOLOGICAL NOTES.—Lung seems somewhat atrophic and there are some vesicular ruptures. One small patch of amyloid found in blood vessel wall. Liver shows slight capillary congestion and granularity of parenchyma. There is a marked blood vessel amyloid deposit not only in interlobular spaces but in intralobular capillaries. Spleen, no trace of splenic tissue recognizable in section. It is composed of more or less eosin-staining material surrounding single, or small collections of round or plasma cells. Kidney shows marked amyloidosis of glomeruli and slight deposit in blood vessel walls and in the increased connective tissue. There is a general moderate fibrosis; irregular tubules; low epithelium and hyaline casts. Heart muscle fibres are small and stain deeply. No amyloid in section. No pigmentation although section is suggestive of brown atrophy. Adrenal is practically negative. There seems to be slightly more connective tissue than normal but parenchyma may be considered normal. At one place in the cortex there are some structures of deep layer included in vesicular layer. This seems like a structural malformation.

NECROSES.

Focal necroses of the spleen affecting chiefly follicular centres but also chords, are not at all uncommon in avian spleens, especially where parasitism occurs, not only with hemic protozoa and embryos, but also with intestinal or visceral nematodes and trematodes.

SPLEEN IN ANEMIA.

The spleen in the anemias shows much less definite change than one would expect. In the secondary form of anemia among mammals one finds a slight excess of pigmentation and an occasional fibrosis but often the size of the organ is recorded as normal. When the impoverished blood seems secondary to skeletal degenerations there is a diffuse or follicular enlargement. In the birds, on the other hand, there is nearly always some grade of enlargement which is due in the well studied examples to a richness of blood cells. There may be a slight increase in follicles, but these bodies are usually small and solid. In two instances a prominence of large endothelial cells was discovered. Pigment is seldom increased, but it may be very excessive.

In the primary anemias little more than the above is to be found. Fibrosis is more evident and perhaps pigmentation less so, but the variations are more of degree than kind. The spleen in leucemia can only be discussed upon the case already reported (q. v.).

FIG. 7.—EUROPEAN BADGER (MELES MELES). PRIMARY AMYLOIDOSIS. THE ENORMOUSLY ENLARGED SPLEEN IS SEEN LYING ACROSS THE STOMACH BELOW THE LIVER, WHICH ORGAN IS EXCEEDED IN SIZE BY IT. ]

SPLEEN IN HEPATIC FIBROSES.

The fibroses of the liver are not infrequently associated with some enlargement of the organ under discussion. At this laboratory hepatic cirrhoses are divided into Portal, Biliary, Fatty, Perilobular and Vascular. By a study of the spleens in these cases a few facts have been obtained. In mammalian portal cirrhoses there is usually a very moderate but definite increase in the size of the spleen due to connective tissue increase in the trabeculæ and reticulum, with very small compact follicles. Among the birds the organ seldom shows more that a moderate congestion and diffuse hyperplasia. In the mammalian biliary cirrhoses there is almost without exception a definite enlargement due to fibrosis and follicular hyperplasia. Among the birds the process is very far from uniform, there being just as often no change, as a congestion and hyperplasia, or as a mild fibrosis; it is notable, however, that pigmentation is commonly met in this class. No noteworthy change is met with in the spleen of fatty hepatic cirrhoses. We have no record of cyanotic induration of the spleen accompanying a similar condition in the liver. When the condition of perilobular hepatic fibrosis has been met a distinct increase of the splenic pigment is usually found. In reviewing the facts in this paragraph one is forced to the conclusion that, with the exception of the frank infective cases, there is no definite relation of the splenic changes to those in hepatic cirrhosis, a fact made perhaps the more significant in view of the idea held in some quarters that the primary change in this pathological process occurs in the spleen.

PERISPLENITIS.

Perisplenitis of an acute or fibrosing variety as a part of peritonitis or as the result of an injury to the splenic region, has been encountered on numerous occasions and offers nothing worthy of comment, but the so-called “sugar-icing” spleen, associated with perihepatitis and general peritoneal thickening, and with an obscure relation to tuberculosis has not been seen. As we shall learn later peritoneal or massive intestinal tuberculosis is not common in the lower animals. A diffuse fibrous thickening of a pearl gray glistening appearance, has occurred in five monkeys harboring the Filaria gracilis in the peritoneum.

TUBERCULOSIS.

In tuberculosis of this organ the capsule is almost invariably thickened over the nodules, but not over the whole organ and rarely in the diffuse variety. There is almost always, however, in this prolonged infectious disease some reaction on the part of the spleen, particularly when several other viscera are involved. In such cases a low grade of general hyperplasia and fibrous tissue increase is found. This is especially true in the Primates and Carnivora in long continued pulmonary tuberculosis, and it is in this form that one does not often see tuberculous lesions proper in the spleen itself. Tuberculosis of the spleen is not very common in adult human beings and domesticated animals, while in the young it is seen in a fairly high percentage of cases. In the wild animals this organ seems much more susceptible to the settling of tubercle bacilli as will be attested by the facts to be cited, and yet there are some conspicuous exceptions to this statement. Just why certain groups, or orders should show splenic tuberculosis very frequently while others fail to do so is far from clear.

The appearance of the lesion is fairly comparable throughout the animal kingdom, variations among the Aves being chiefly in the more frequent occurrence of the diffuse tuberculous splenitis. Miliary, caseous and conglomerate masses occur separately or together and without very distinct relation to other pathological involvements.

The relative incidence of tuberculosis in the spleen is set forth in the section devoted to this infection, but may be mentioned here in a general way. The organ is about equally susceptible to the disease in mammals and birds according to the figures, but the high percentage for the former is due to the frequency with which tuberculosis is met in the Primates. With this order deducted there is no doubt that the avian spleen has a greater vulnerability for the tubercle bacillus than has the mammalian organ. Rodentia as a mammalian order stand next to the Primates, whereas the Carnivora and Ungulata relatively seldom show splenic tuberculosis. Among the Aves one finds that Columbæ, Galli and Accipitres have the highest splenic susceptibility, but beyond this one hardly dare venture because of the irregularity in the number of specimens seen at autopsy. Suffice it to say that a greater number of cases of tuberculosis are seen in the spleen of the class for which the intestinal origin of tuberculosis appears most important.

In the cases of actinomycosis and its congeners, such as the Kangaroo maxillary mycosis, which we have seen at the Garden, no specific changes have been seen in the spleen, unless a single or double nodule of the same variety as the original focus may be considered specific. Such was found in two cases, one a tapir with low grade inactive actinomycosis, the other a kangaroo with maxillary streptothricosis. Two deer came to autopsy with a gross picture suggestive of anthrax; no bacilli could be found in the semifluid spleen, but a member of the hemorrhagic septicemia group was found. The latter group of infections has been fairly well represented, although not in epizoötic form, and the almost invariable splenic change has been that already discussed as diffuse splenitis. Three secondary tumors are recorded, two cancers and one renal adenoma.