Part 48

════════════════════╤══════════════════════════════════════════════════════ Order Family │ Visceral Distribution │ │ │ ────────────────────┼─────────┬──────┬─────────┬──────┬─────┬─────┬──────── „ „ │Intestine│Kidney│ Serous │Bones │Brain│Heart│Pancreas │ │ │membranes│ and │ │ │ │ │ │ │joints│ │ │ │ │ │ │ │ │ │ ────────────────────┼─────────┼──────┼─────────┼──────┼─────┼─────┼──────── Primates │ 30│ 84│ 70│ 2│ 2│ 7│ 3 Simiadæ │ 2│ 1│ 1│ │ │ │ Cercopithecidæ│ 24│ 76│ 63│ 2│ 2│ 7│ 2 Cebidæ │ 4│ 7│ 6│ │ │ │ 1 Lemures, Lemuridæ │ 2│ 7│ 1│ │ │ │ 1 Carnivora │ 1│ 4│ 3│ 1│ │ │ Rodentia │ 1│ 2│ 2│ 1│ │ │ Ungulata │ 1│ 2│ 7│ │ │ │ Equidæ │ │ │ │ │ │ │ Bovidæ │ 1│ 1│ 1│ │ │ │ Cervidæ │ │ │ 5│ │ │ │ Camelidæ │ │ 1│ 1│ │ │ │ Proboscidea │ │ │ │ │ │ │ ────────────────────┼─────────┼──────┼─────────┼──────┼─────┼─────┼──────── Totals for Mammalia │ 35│ 99│ 83│ 4│ 2│ 7│ 4 Passeres │ 4│ │ 4│ │ │ │ Picariæ │ 4│ 1│ 3│ 1│ │ │ Psittaci │ 12│ 6│ 6│ │ │ 1│ Loriidæ │ 1│ 1│ 1│ │ │ │ Cacatuidæ │ │ 1│ 1│ │ │ 1│ Psittacidæ │ 11│ 4│ 4│ │ │ │ Striges │ │ │ 3│ │ │ │ Accipitres │ 4│ 3│ 6│ │ │ 2│ Columbæ, Columbidæ │ 16│ 13│ 20│ │ │ 1│ Galli │ 20│ 7│ 15│ │ │ │ 1 Phasianidæ │ 10│ 2│ 6│ │ │ │ 1 Cracidæ │ 10│ 5│ 7│ │ │ │ Megapodidæ │ │ │ 2│ │ │ │ Fulicariæ │ 3│ 3│ 4│ │ │ │ Hemipodii │ 1│ 1│ 1│ │ │ │ Alectorides │ 3│ 3│ 7│ │ │ │ Odontoglossæ │ 1│ │ │ │ │ │ Anseres │ 3│ 4│ 4│ │ │ │ Struthiones │ │ 1│ 1│ │ │ │ Crypturi │ 2│ 1│ │ │ │ │ ────────────────────┼─────────┼──────┼─────────┼──────┼─────┼─────┼──────── Totals for Aves │ 73│ 43│ 74│ 1│ 0│ 4│ 1 ────────────────────┼─────────┼──────┼─────────┼──────┼─────┼─────┼──────── Grand Totals │ 108│ 142│ 157│ 5│ 2│ 11│ 4 ────────────────────┴─────────┴──────┴─────────┴──────┴─────┴─────┴──────── See page 484, for description of tabulation. For meaning of italics see foot note Table 1. These and figures set opposite them are cases not percentages.

It is generally conceded that the principal and only significant routes of origin for tuberculosis are via the respiratory and alimentary tracts. The criteria upon which to decide the route that has been followed are by no means definite and may not be for any given case unexceptionable. In birds the alimentary tract is conceded to be the important one, while in mammals an aerogenic route is believed to be the rule. However, since feeding experiments have shown that tubercle bacilli can gain the lungs by passing through the intestinal wall and abdominal lymphatics without leaving gross traces, the decision that one or the other route has been taken may be erroneous, and statistics therefore can often be fallacious. It is usually the rule to assume that the oldest or best developed lesions occur where the originally settled organisms exerted their maximum effect. The questions of infection-path and of original lesion not having been settled it is obvious that decision as to the route must be in the nature of an estimate. With these limitations in mind I have divided the cases into probable respiratory and alimentary origins according to the following criteria. Where the lesions were wholly respiratory or within the lymph glands of the trachea and bronchi the decision was not so difficult. Predominance of the pulmonary disease with recent lesions in other organs was taken to indicate an aerogenic origin. The chronic ulcerative or fibrous pulmonary lesions were also ascribed to those beginning in the lungs. The alimentary tract was considered for this purpose as beginning in the tonsillar area and ending at the anus. This is as I understand the customary teaching. When the lymph nodes of the alimentary area were advanced in the process, the intestinal method was held responsible. It is of course not to be forgotten that organisms coughed up from the lungs and swallowed may be responsible for lesions within the alimentary system. However, a predominance of intestinal, splenic, hepatic and lymphatic lesions caused me to place the case with those originating from the alimentary tract. Granting the limitations of our knowledge, of the criteria and of my own judgment, it is noteworthy that the results of this division of the table are not contradictory to the usual teaching, the most conspicuous being the predominance of the alimentary infection of Aves and in the order Primates, whereas the pulmonary route has the highest figures for the Ungulata.

The next subdivision of the table concerns the gross pathological type. Beginning with the most acute form, the acute miliary, progression is made in terms of chronicity—then following in order the massive caseous form including caseous pneumonia, the caseous miliary or nodular form so well represented by the monkey, then the fibroulcerative type such as one encounters in human consumption, including also forms in which fibrosis predominates, and lastly the rather uncommon pearl disease. This classification has been relatively easy to follow and can be readily imagined by the reader. There are of course intermediate cases or transition forms and there have been instances partaking of more than one character. The groupings present only gross appearances and, with few exceptions, are not to be taken as direct indications of type incidence in special groups.

Visceral distribution is shown in the last gross section of the table; single cases or unusual locations are not tabulated but will be separately discussed. The visceral distribution is made upon evident gross lesions or their discovery in organs whose condition suggested the need of microscopic study for confirmation. The figures in the table will be reviewed first upon the incidence as a whole and then between classes and orders. This will be succeeded by an analysis of the particulars for each order and then for each of the pathological headings.

TOTAL AND CLASS INCIDENCE.

The autopsies upon 5,365 animals have revealed the existence of tuberculosis in 492, a percentage of 9.1. This means that lesions due to the _Bacillus tuberculosis_ were present, but they were not always the cause of death, since many specimens have been executed and others have had sufficient pathology to kill, aside from the tuberculous changes. Deaths due to the disease alone are difficult to estimate, but seem to be about 325 or 6 per cent. These figures, while they represent the total incidence, lose considerably in significance when the factors are analyzed. Mammalian incidence is 14.7 per cent., Avian 6.2 per cent., but the former is based upon figures obtained from six of twelve orders numbering 1,860 animals, whereas the latter represent the cases in fourteen of twenty orders numbering 3,505 birds. The percentages are considerably increased by high figures for a few orders, Primates, Lemures, Columbæ for examples. There are missing from the list very few orders of which we have any notable number of autopsies, Marsupialia and Herodiones being the only important ones; it would seem that these orders have a high resistance to the disease.

Investigation into the origin of the disease in mammals and birds shows with definiteness the preponderance of the alimentary route influence in the latter, but for the former the figures cannot be said to be conclusive. The bird excretes large numbers of bacilli with the feces thereby soiling the feed and the ground. This is due to the frequency of intestinal open lesions and to the really enormous numbers of bacilli which are in the morbid tissue. I think it can be said with safety that, other things being equal, the bird excretes bacilli constantly and in greater numbers than does the mammal, and that in physically comparable lesions there are more bacilli in the avian than in the mammalian.

The inconclusive figures for the origin of the disease in the mammal can be clarified very little by the subtraction from the tables of the figures for the very susceptible Primates. By doing this it would seem that the respiratory route dominates as 43 to 29, whereas if the reasonably susceptible Lemures be also deducted the ratio becomes as 38 to 15. It would seem that the evidence favors the aerogenic route in the mammal.

PATHOLOGICAL TYPES.

An inquiry into the gross pathological types reveals at once the frequency with which the nodular and massive caseous forms appear. If the number of cases be reduced to percentage it will be found that 59 per cent. of all specimens presented the nodular variety and 26.6 per cent. the massive caseous form. These large figures (equaling when combined 85 per cent.) coupled with the fact that only 12 per cent. of the total were fibroulcerative and 1.8 per cent. of the pearl type, would seem to indicate that the nodular and massive caseous processes are the lesions to be expected in wild animals. Furthermore, if these nodular and caseous forms speak for recent infection or acuteness of the morbid process, it would seem that wild animals have a low tissue resistance to tuberculosis. It is a widespread belief, in some degree well supported, that a disease new to an animal species is highly fatal and that the survival of the race depends upon an active self- immunization or the survival of the pathologically least susceptible. If tuberculosis be a disease of civilization, these figures would suggest that it is absent in nature. As a further support of this idea it can be said that with the exception of two cases in ungulates, no fibroid tuberculosis, approaching the quiescent type as seen in man and rarely in domestic animals, was encountered. Very rarely calcareous deposits will be found in both simian and ungulate lesions but these need not indicate a tendency to general healing although at that place the process may be inactive. The bird uses considerable fibrous tissue in the construction of its tuberculous mass but fibrosis never masters the situation with the formation of scar tissue sufficient to wall off the process. Pearl disease, a fibrocaseous condition, is not a healing fibroid procedure and is, in our material, of no numerical significance.

VISCERAL DISTRIBUTION.

The distribution of the morbid lesions in the viscera presents some interesting features. In the first place the data leave no doubt that the most susceptible tissue in the wild animal body is, as in the case of human and domestic animals, the lung. The susceptibility of this organ in the two classes is however a different matter since in the mammal 91.4 per cent. show pulmonary lesions while only 53.7 per cent. of birds are so affected. Part of the reason for this appears in the figures for the principal abdominal organs, of which the liver and spleen occupy the prominent places. The mammalian livers show 58.2 per cent., the avian 80.3 per cent.; 67.5 per cent. of mammalian spleens, 68.0 per cent. of avian spleens have tuberculous lesions. The figure for the mammalian spleen is distorted because of the peculiar susceptibility of this organ in the monkey, it being conspicuously free of lesions in most mammalian orders. The intestines presented discernible lesions in practically 40 per cent. of birds but only in 13.5 per cent. of mammals. Renal involvement was found in 38.4 per cent. of mammals and 22.9 per cent. of birds.

A study of the changes in the serous surfaces is complicated by the difference of anatomy in the two classes. The mammal has separate closed serous sacs well guarded against invasion from mucous surfaces whereas in the bird the air sacs and serous cavities are closely related, the latter being loosely applied to viscera they are intended to cover. Moreover in Aves direct infection of the air sacs seems a definite possibility. Notwithstanding the fact that the bird’s sacs and serous surfaces appear so open to infection there is no great preponderance of lesions within them—Aves 39.3 per cent. Mammalia 32 per cent. The lymph nodes were tabulated as a tissue rather than according to location, the latter method being found profitable for discussion in a few orders only. As might be expected the abundant lymph nodes of the mammal were affected out of all proportion to those in the bird. These matters will be discussed later. The remaining figures on the table have no comparative value.

ORDINATE CHARACTERISTICS.

The Primates as an order have shown low resistance to tuberculosis, a fact well known to general observation. How much this is due to the unsanitary surroundings to which these naturally free active beasts are subjected, in catching, transporting and storing for sale, must at present remain conjectural, but they are probably infected with ease as our experience in this laboratory suggests. Desiring a tuberculous monkey for certain tuberculin tests, I injected one hundredth of a milligram of a human culture, known to produce definite lesions in rabbits; the animal died in three months with advanced general tuberculosis. The unexpected and interesting feature of our figures is the susceptibility of different families within the order. The Old World monkeys, Simiadæ and Cercopithecidæ have a combined incidence two and one-half times as great as the New World Cebidæ, and the marmosets had no tuberculosis at all in the thirty-two specimens. Possibly this is a matter of transportation and handling, which reduces the resistance and offers chance to infect apes and baboons. The New World capucin monkeys have their exposure too since many of them are household pets before the Garden receives them. Their usual life in captivity is however shorter than that of Old World varieties, they therefore being exposed to infection for a shorter time. It would seem however that American Primates are more resistant to the disease than African and Australasian.

The form of tuberculosis to which this order is liable is well described in text-books, it being so characteristic that the term “monkey tuberculosis” is used to distinguish it. The purpose of the term is to compare the lesions with certain cases of generalized tuberculosis in children. It is characterized by a nodular involvement of the liver and of the spleen particularly, sometimes also of the lungs but in fatal cases the last organ is commonly the seat of massive caseation or caseous pneumonia. The prominence of the pulmonary lesions often makes a decision of origin difficult since important changes may be found in the liver and abdominal nodes. Blair at New York, and Rabinowitsch at Berlin are of the impression that many cases of monkey tuberculosis start by pharyngeal and tonsillar infection because they found cervical adenitis so commonly. Our records and specimens would support this idea in only fourteen instances and I am of the impression that the lower intestinal route is more often responsible, even to a higher figure than is recorded in the table. This view is based upon the frequent occurrence of enlarged glands in the mesentery, retroperitoneum and posterior mediastinum, in the latter location being quite as prominent if not more so than in the bronchial and tracheal area. Occasionally deposits of calcareous matter will be found in old caseous glands but in such animals there has always been some other spot of activity of tuberculosis. The frequency with which the liver and spleen are affected gives opportunity for hematogenic spread, a method of no small importance in the opinion of Eber. The chronic ulcerative form is quite well displayed in monkeys, interestingly enough to cite an illustrative case at the end of this division of the discussion. Five cases of distinct chronic cavitation were encountered; several small recent cavities were found in the massive caseous pneumonic cases. The two acute miliary cases and one of the pearl type will be discussed briefly on a later page.

Despite the prominence of the liver, spleen and lymph nodes, the lungs stand ahead of all others by a safe margin of visceral incidence. The spleen stands in the third place in this order and in the next, Lemures, but in no other mammalian group does this organ occupy so prominent a position. The susceptibility of lymphatic tissue in the monkey is further illustrated by the large number of cases showing lesions in lymph nodes. It is rather striking however that our material showed very few active ulcerations in the lymphoid plaques of the intestinal wall nor indeed do the intestines present a large numerical involvement. Serous membrane tuberculosis is chiefly that of the pleura, upon which early precaseous tubercles are frequently found, usually in conjunction with pulmonary disease. Tuberculous peritonitis of the plastic and nodular variety occurred only six times, though light adhesions to nodules in the liver and spleen were quite common. Pericarditis was found five times, in three of which there was myocardial disease; which of the two was primary was not indicated in the notes but from present reading it would seem that the heart muscle was involved first.

The next order, Lemures, has a susceptibility of about half that of the monkeys judging by the percentage incidence. Analytically the members of this group react quite like the preceding order in having the same types of origin, pathology and organic distribution. Since they are so close zoologically, present similar lesions and are tested in the same manner as the monkeys, we group them together and shall proceed to discuss special cases of interest in both orders.

Special Cases in Primates and Lemures. Acute general miliary tuberculosis occurred thrice in Old World and once in New World monkeys. The first case took its origin in a caseous gland in the bronchotracheal area, the lung showing a minor degree of involvement with milia but no older process. The second took its origin in the mesenteric area and the organs of this section of the body were most affected. The only case in the Cebidæ seemed to be of intestinal origin since an acute plastic peritonitis with fluid exudate accompanied the generally miliary disease.

Pearl disease of the bovine type has been encountered on four occasions but it cannot be said to have developed to the state of perfection seen in the cow. There is lacking the masses of nodules growing together in a fungoid character usually seen on the pleura and peritoneum. The monkey form is in isolated nodules of gray-yellow color which may show caseous centres. The visceral lesions are in firm separate areas not tending to soften or coalesce. Two of these monkeys died from recent pulmonary exacerbations. From one of the cases a bovine bacillus, judging from culture and rabbit virulence, was isolated.

As a good example of monkey tuberculosis, illustrating at the same time a chronic ulcerative pneumonitis with cavitation, the following case is cited:

Green Monkey (_Cercopithecus callitrichus_) ♀ . Was coughing and drooping for two days before death. Chronic ulcerative tuberculosis of lungs with cavity formation; early conglomerate tuberculosis of liver; conglomerate caseous tuberculosis of spleen; early conglomerate tuberculosis of ileum (Peyer’s patches); acute catarrhal enteritis; miliary tuberculosis of right kidney. The animal is well preserved, sleek, with a moderate amount of fat. The left pleura is largely obliterated by adhesions in the lower portion. As lung is freed it is torn, showing a cavity measuring 3 × 3 × 4 cm., which is filled with a curdy gray material. Cavity has well defined walls. Rest of lower lobe in which this cavity lies is solidified, red and edematous and contains numerous conglomerate tubercles. Upper lobe practically free of tubercles; shows compensatory emphysema. The right lung closely resembles the left but lacks the cavity. The liver is enlarged, soft and friable, of red color, spotted yellow. Serous and section surfaces show closely packed early conglomerate tubercles. The spleen is of normal size, soft, has red pulp with large conglomerate tubercles which project slightly on the capsule. The kidneys are apparently normal except for the presence of two or three subcapsular large, solitary tubercles in the right organ. The duodenum has thickened walls, mucosa bright, brilliant scarlet hue. In the ileum the walls are thickened, mucosa bright red, agminated follicles hyperplastic elevated and display several (4–12) miliary tubercles. These may be seen shining through on the serous surface but there is no peritoneal tuberculosis. No ulceration of Peyer’s patches. Contents of large intestine is rather dry and here the mucosa shows exaggerated rugæ which cannot be smoothed out. Walls are thickened, and ulceration, while suggested, cannot surely be determined.

An interesting case of primary tuberculosis in the larynx detected at postmortem after a tuberculin injection is as follows:

Black and White Lemur (_Lemur varius_) ♂ . Miliary tuberculosis of larynx; perilaryngitis and retropharyngeal lymphadenitis. Killed because of unsatisfactory chart after injection of tuberculin. The only tuberculous lesion to be found in the body, which is in excellent shape, is in and about the larynx. The lesions within are on the epiglottis, false and true vocal cords and the main ventricle. On either side of the root of the epiglottis, there are a few recent tubercles. The lesion in the retropharyngeal lymphatics is recent and diffuse. This is probably primary as it is not known that the retropharyngeal glands drain to or from the larynx. About the lesions on the laryngeal mucosa there is an area of congestion probably due to the tuberculin injection.