Chapter XXVII: Section XVII: The Communicable Diseases—part I (1)

TUBERCULOSIS.

Nearly all infectious diseases have either a limited natural zoological distribution or are encountered chiefly in one order or division. Thus typhoid fever is peculiar to man, hog cholera to swine, foot-and-mouth disease to cows. A second group, including for example anthrax, variola, hemorrhagic septicemia and malignant edema, is somewhat less specific, and may occur in several varieties. There is no more widespread, important infection, zoologically, economically and hygienically, than tuberculosis, and it would seem that all kinds of vertebrates are subject to it. Its manifestations too, are sufficiently similar to support the idea that there must have been originally a common ancestor of the viruses which we now designate separately by a term to indicate their immediate source (human, avian, etc.), and moreover it has been shown that any of the artificially separated varieties or subspecies may under certain circumstances infect all zoological families.

There is, however, a varying resistance to the tubercle bacillus, certain zoological groups standing out preëminently as more or less susceptible to it. There is also a tendency for each animal group to present features more or less peculiar to itself, but nevertheless the characteristics, both gross and minute, of the disease caused by the _Bacillus tuberculosis_ are sufficiently similar to permit close analogy and to establish a diagnosis when the bacteria are found.

The data collected at this Garden are well suited to elucidate the susceptibility of wild animals under captive conditions and to illustrate the nature of lesions in them. Perhaps they do not offer a perfect cross section of zoological distribution of tuberculosis because of the predominance in the display of birds, of monkeys and of ungulates, but the figures will be found significant in certain respects. Such records cannot be compared with those obtained for domesticated animals in farms or breeding places, nor can our material be used to show the incidence for individual species, such as cows, dogs and the like, in a manner commonly used in veterinary literature. Those who are interested in this phase of the problem can find in Lubarsch- Ostertag’s _Ergebnisse_, 1917–18, No. 2, a summary by Eber of all recent literature, covering nearly 1,700 references, which really amounts to a review of all modern knowledge of tuberculosis in the lower animals. The article does not, however, attempt to compare or contrast the incidence per order or family in wild varieties since little information is available on these points. There are no reliable data concerning the existence of tuberculosis in the wild. It is noted in the report of the British Tuberculosis Commission that monkeys were received with this disease; Eber mentions that wild swine from a private preserve presented undoubted evidence of tuberculosis and another similar experience with pheasants, but these and other citations can give no proper estimate of exact conditions nor allow a decision that the infection exists at all under natural environment for in all cases the association with human beings or domesticated animals cannot be excluded. Tuberculosis is usually described as a disease of civilization and its incidence surely varies directly with crowding.

THE TABLE.

Description of Table 23. The study of our autopsy records was begun by the preparation of the accompanying table, which is based first upon the zoological classification per order with subdivisions for families where there are sufficient examples within important orders, and second, upon percentage of total cases. For the analysis of the pathological types, headings of probable origin, gross anatomical lesions and visceral distribution were then made. The first vertical column shows the total autopsies per order, and where families are given, for each of them. In three instances Primates, Ungulata and Galli, not all families are represented, so that the total for the order is greater than that for the subdivisions quoted. It is noteworthy that we have had no tuberculosis among nine families of ungulates; this will be discussed later. The second column gives the total cases of tuberculosis for the order and family, respectively, followed by a third line of percentages. For the analysis of the pathology in these animals all the protocols were reviewed. Forty-eight of them being found unsuitable, deductions were made according to the natural group, thereby leaving the number shown in the fifth column for separation according to origin and type. Analyses in the succeeding columns are made upon number of cases and not upon percentages, because of the confusion arising from small decimals. The actual relationships will be pointed out in the notes. Percentage is not so necessary because comparisons and contrasts are usually made with classes or orders where the figures are comparable.

TABLE 23.
_Analytical Table Showing Incidence of Tuberculosis per Order and for
Some of the Principal Families, to Which are Added Columns Showing
Probable Origin of Infection, Pathological Type of the Disease and the
Visceral Distribution of the Morbid Process._

════════════════════╤═════════╤════════════╤══════════╤════════════ Order Family │ No. of │ Cases of │Percentage│ Cases not │autopsies│Tuberculosis│ │sufficiently │for order│ │ │ described │or family│ │ │for analysis ────────────────────┼─────────┼────────────┼──────────┼──────────── „ „ │ „ │ „ │ „ │ „ │ │ │ │ │ │ │ │ │ │ │ │ ────────────────────┼─────────┼────────────┼──────────┼──────────── Primates │ 498│ 192│ 38.5│ 8 Simiadæ │ 7│ 3│ 43.│ 0 Cercopithecidæ│ 353│ 171│ 48.4│ 8 Cebidæ │ 106│ 18│ 16.9│ 0 Lemures, Lemuridæ │ 86│ 23│ 26.7│ 3 Carnivora │ 481│ 17│ 3.5│ 4 Rodentia │ 199│ 5│ 2.5│ 0 Ungulata │ 365│ 35│ 9.6│ 2 Equidæ │ 11│ 1│ 9.│ 0 Bovidæ │ 123│ 12│ 9.7│ 1 Cervidæ │ 171│ 19│ 11.1│ 1 Camelidæ │ 25│ 3│ 12.│ 0 Proboscidea │ 3│ 2│ 66.│ 0 ────────────────────┼─────────┼────────────┼──────────┼──────────── Totals for Mammalia │ [97]1860│ [97]274│ [97]14.7│ 17 Passeres │ 1355│ 18│ 1.3│ 6 Picariæ │ 87│ 11│ 13.│ 0 Psittaci │ 698│ 38│ 5.4│ 3 Loriidæ │ 24│ 3│ 12.5│ 0 Cacatuidæ │ 80│ 7│ 8.7│ 1 Psittacidæ │ 585│ 28│ 4.8│ 2 Striges │ 133│ 6│ 4.5│ 3 Accipitres │ 196│ 11│ 5.6│ 1 Columbæ, Columbidæ │ 157│ 50│ 32.│ 5 Galli │ 299│ 42│ 14.│ 5 Phasianidæ │ 252│ 22│ 8.3│ 3 Cracidæ │ 38│ 17│ 44.│ 1 Megapodidæ │ 5│ 3│ 60.│ 1 Fulicariæ │ 35│ 9│ _27._│ 0 Hemipodii │ 2│ 1│ _50._│ 0 Alectorides │ 37│ 10│ _27._│ 2 Odontoglossæ │ 6│ 2│ _33._│ 1 Anseres │ 317│ 16│ 5.│ 5 Struthiones │ 32│ 3│ _9.4_│ 0 Crypturi │ 5│ 2│ _40._│ 0 ────────────────────┼─────────┼────────────┼──────────┼──────────── Totals for Aves │ [97]3505│ [97]219│ [97]6.2│ 31 ────────────────────┼─────────┼────────────┼──────────┼──────────── Grand Totals │ [98]5365│ [98]493│ [98]9.1│ 48 ────────────────────┴─────────┴────────────┴──────────┴────────────

════════════════════╤════════╤══════════════════════╤═══════════════ Order Family │Net no. │ Probable origin │Pathological Type │of cases│ │ │ in │ │ │analysis│ │ ────────────────────┼────────┼──────────┬───────────┼───────┬─────── „ „ │ „ │Pulmonary-│Intestinal-│ Acute │Massive │ │aerogenic │ lymphatic │Miliary│caseous │ │ │ │ │ │ │ │ │ │ ────────────────────┼────────┼──────────┼───────────┼───────┼─────── Primates │ 184│ 86│ 98│ 3│ 52 Simiadæ │ 3│ 3│ │ │ 2 Cercopithecidæ│ 163│ 76│ 87│ 2│ 46 Cebidæ │ 18│ 7│ 11│ 1│ 3 Lemures, Lemuridæ │ 20│ 6│ 14│ │ 5 Carnivora │ 13│ 6│ 7│ │ 1 Rodentia │ 5│ 3│ 2│ │ 3 Ungulata │ 33│ 27│ 6│ │ 6 Equidæ │ 1│ │ 1│ │ 1 Bovidæ │ 11│ 10│ 1│ │ 1 Cervidæ │ 18│ 14│ 4│ │ 4 Camelidæ │ 3│ 3│ │ │ Proboscidea │ 2│ 2│ │ │ ────────────────────┼────────┼──────────┼───────────┼───────┼─────── Totals for Mammalia │ 257│ 130│ 127│ 3│ 67 Passeres │ 12│ 9│ 3│ │ 5 Picariæ │ 11│ 1│ 10│ │ 2 Psittaci │ 35│ 13│ 22│ 1│ 9 Loriidæ │ 3│ 1│ 2│ │ 1 Cacatuidæ │ 6│ 4│ 2│ │ 1 Psittacidæ │ 26│ 8│ 18│ 1│ 7 Striges │ 3│ 3│ │ │ 1 Accipitres │ 10│ 5│ 5│ │ 2 Columbæ, Columbidæ │ 45│ 10│ 35│ │ 12 Galli │ 37│ 10│ 27│ │ 12 Phasianidæ │ 19│ 2│ 17│ │ 4 Cracidæ │ 16│ 7│ 9│ │ 7 Megapodidæ │ 2│ 1│ 1│ │ 1 Fulicariæ │ 9│ 1│ 8│ │ 1 Hemipodii │ 1│ 1│ │ │ 1 Alectorides │ 8│ │ 8│ │ 2 Odontoglossæ │ 1│ │ 1│ │ Anseres │ 11│ 2│ 9│ │ 4 Struthiones │ 3│ 3│ │ │ Crypturi │ 2│ │ 2│ │ ────────────────────┼────────┼──────────┼───────────┼───────┼─────── Totals for Aves │ [99]188│ 58│ 130│ 1│ 51 ────────────────────┼────────┼──────────┼───────────┼───────┼─────── Grand Totals │ [99]445│ 188│ 257│ 4│ 118 ────────────────────┴────────┴──────────┴───────────┴───────┴───────

════════════════════╤════════════════════════╤════════════════════════ Order Family │ Pathological Type │ Visceral Distribution │ │ │ │ │ │ ────────────────────┼───────┬──────────┬─────┼─────┬─────┬──────┬───── „ „ │Nodular│ Chronic │Pearl│Lungs│Liver│Spleen│Lymph │caseous│ fibrous │type │ │ │ │nodes │ │ and │ │ │ │ │ │ │ulcerative│ │ │ │ │ ────────────────────┼───────┼──────────┼─────┼─────┼─────┼──────┼───── Primates │ 108│ 16│ 5│ 173│ 122│ 149│ 145 Simiadæ │ │ │ │ 3│ 2│ 3│ 3 Cercopithecidæ│ 96│ 16│ 3│ 156│ 111│ 136│ 128 Cebidæ │ 12│ │ 2│ 14│ 9│ 10│ 14 Lemures, Lemuridæ │ 15│ │ │ 17│ 14│ 17│ 12 Carnivora │ 8│ 4│ │ 11│ 4│ 2│ 6 Rodentia │ 2│ │ │ 4│ 2│ 2│ 4 Ungulata │ 1│ 24│ 2│ 28│ 7│ 3│ 25 Equidæ │ │ │ │ │ │ │ 1 Bovidæ │ 1│ 9│ │ 9│ 4│ 2│ 7 Cervidæ │ │ 13│ 1│ 17│ 2│ │ 14 Camelidæ │ │ 2│ 1│ 2│ 1│ 1│ 3 Proboscidea │ │ 2│ │ 2│ │ │ ────────────────────┼───────┼──────────┼─────┼─────┼─────┼──────┼───── Totals for Mammalia │ 134│ 46│ 7│ 235│ 149│ 173│ 192 Passeres │ 7│ │ │ 9│ 5│ 5│ Picariæ │ 8│ │ 1│ 2│ 9│ 6│ 1 Psittaci │ 25│ │ │ 18│ 24│ 14│ 2 Loriidæ │ 2│ │ │ 3│ 3│ 1│ Cacatuidæ │ 5│ │ │ 5│ 5│ 2│ Psittacidæ │ 18│ │ │ 10│ 16│ 11│ 2 Striges │ 2│ │ │ 3│ 3│ 2│ Accipitres │ 7│ 1│ │ 8│ 6│ 8│ 1 Columbæ, Columbidæ │ 33│ │ │ 24│ 40│ 34│ 1 Galli │ 24│ 1│ │ 20│ 34│ 29│ 2 Phasianidæ │ 15│ │ │ 7│ 18│ 15│ 1 Cracidæ │ 8│ 1│ │ 12│ 15│ 13│ Megapodidæ │ 1│ │ │ 1│ 1│ 1│ 1 Fulicariæ │ 8│ │ │ 4│ 8│ 8│ 1 Hemipodii │ │ │ │ 1│ 1│ 1│ Alectorides │ 6│ │ │ 4│ 8│ 7│ 2 Odontoglossæ │ 1│ │ │ │ 1│ 1│ Anseres │ 5│ 2│ │ 4│ 7│ 8│ 1 Struthiones │ │ 3│ │ 3│ 2│ 3│ 2 Crypturi │ 2│ │ │ 1│ 2│ 2│ ────────────────────┼───────┼──────────┼─────┼─────┼─────┼──────┼───── Totals for Aves │ 128│ 7│ 1│ 101│ 151│ 128│ 13 ────────────────────┼───────┼──────────┼─────┼─────┼─────┼──────┼───── Grand Totals │ 262│ 53│ 8│ 336│ 300│ 301│ 205 ────────────────────┴───────┴──────────┴─────┴─────┴─────┴──────┴─────

════════════════════╤══════════════════════════════════════════════════════ 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:

FIG. 51.—BOVINE TUBERCULOSIS IN THE MONKEY. THIS SPECIMEN SHOWS THE
BOVINE PEARL DISEASE ON THE COSTAL PLEURA, AND SERVES AS WELL TO
ILLUSTRATE THE NODULAR TUBERCLES COMMONLY FOUND IN THE SPLEEN OF ALL
PRIMATE TUBERCULOSIS.
]

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.

Local lymphatic tuberculosis of comparative interest was encountered a few times. Three cases of cervical adenitis, large enough to be visible, were seen, of which one broke down about two weeks before death, and discharged. The others did not ulcerate through the skin but, contrary to the usual rule for the human being, remained as isolated glands only lightly adherent to one another where they lay adjacent. There was also seen an ulcerating tuberculous lymph node in the groin of one monkey, the animal having rather pronounced abdominal and pelvic tuberculosis. Two instances of tonsillar tuberculosis are recorded, in both of which the lesion was of some duration and associated with caseation in the lymph node lying immediately behind and below it. A Guinea Baboon (_Papio sphinx_) had as an unusual part of his general tuberculosis, an active caseopurulent collection in the antrum of Highmore, which attacked the upper maxilla and immediately adjacent muscle; tubercle bacilli could be demonstrated.

One of the cases of nodular or massive peritoneal tuberculosis is quite like the tumor-forming variety of human adolescents; it is as follows:

Reddish Macaque (_Macacus rufescens_). Caseous tuberculosis of
mesentery and spleen; miliary tuberculosis of lungs, pleura and liver;
chronic myocarditis. The lymphatic glands of the posterior and
superior mediastinum and bronchi are slightly enlarged, soft and
anthracotic but do not show any tuberculous change. Both lungs are
riddled with small, firm, gray miliary tubercles, some surrounded by a
clear mantle of connective tissue. The intervening lung is practically
normal. Pleura over base of right lung on both surfaces shows small,
pale miliary tubercles. The liver contains various sized miliary
tubercles. There is a large caseous mass in posterior end of spleen
with adhesions to kidney, stomach and colon. Retroperitoneal glands
are much enlarged, firm, homogeneous—probably tuberculosis of a
different type. Lesser omentum contains one caseous gland. Few caseous
glands in great omentum. In the right iliac region there is a large
mass involving many coils of intestine. It is found to arise probably
from the ileocecal glands and can be traced along the mesentery to the
central lymphatic stalk. The mass involved the tissues of the
mesentery and surrounds many coils of intestine. Cecum and first part
of colon can be traced over its right side. Rectum is free except on
right side where it is lightly attached to the mass. Epicardium is
gray and irregularly thickened and the muscle just beneath serous
membrane is pale and streaked with red lines.

There have been three cases of tuberculosis of the internal male genital area, one of which was suspected of having been the primary seat of the disease; it was described on page 315. The other two could have been secondary since other points of morbid change were as old or older. One of these cases formed a tumor as large as a goose egg at the vesical neck, obstructing the flow of urine and blocking up the seminal vesical, in consequence of which paralytic distention occurred in the bladder while the vesicles were tightly filled with inspissated semen. A case of Fallopian salpingitis has also been cited. Two instances of cerebral tuberculomata have already been described.

Carnivora. This order has the reputation of being quite resistant to the tubercle bacillus, based upon the relative infrequency among cats and dogs in contrast to cows and swine. Some veterinary statistics cite the incidence up to 5 per cent., and occasional references may be found to tuberculosis in circus lions and tigers. Our records would suggest that in gardens the wild varieties of this order have about as much of the infection as the domestic carnivores, 3.5 per cent. The group is made of six Felidæ, one Viverridæ, three Canidæ, six Procyonidæ, and one Ursidæ. The first family includes a lion, tiger, a jaguar and three smaller cats. The Canidæ are all small foxes. The Procyonidæ are all coatis. The features of this order are the occurrence of the fibroulcerative variety with cavitation in the Felidæ and the caseous nodular abdominal and glandular disease in the coatis. All these animals, even those of the last named variety and pathological type, tend to show some tissue resistance to the tuberculous disease. Connective tissue activity is characteristic of the process, considerable distortion being produced by the fibrosis. This feature is borne out where the tissues are studied microscopically. Definite milia are sometimes found, but they consist of epithelioid and round cells with imperfect caseation, giant cells being often missing. About the miliary tubercles a diffuse and not essentially specific tuberculous granulation tissue is found, mixed with which is much connective tissue growth. The fibrotic adhesion-forming serous membrane tuberculosis of carnivores seems worthy of emphasis by the citing of a case in point. White nosed coati (_Nasua narica_), was received in poor condition and died in a few days. Upon dissection a slightly turbid yellowish fluid was found to occupy what remained of the peritoneal cavity which was reduced in size by dense adhesions of the intestines into an inflammatory mass. The omentum was a diffuse thickened apron, also beset with fine tubercles, lying over the mass. Fine young tubercles could also be found upon the intestines and liver while the mesenteric lymph nodes were early in caseation; thoracic organs not infected.

One of the most interesting cases concerned hypertrophic osteitis in a chronically tuberculous lion; the feet are discussed on page 346. This process was described by Marie for human beings many years ago, and was reported in dogs by Cadiot[100] in 1912. This beast was one of five large cats which have died from tuberculosis in its chronic ulcerative form. Three of the cats, one fox and the bear showed definite cavitations of a ragged loculated form. The cavities were usually of the multiple variety and were found in the posterior, that is lower lobe.

Rodentia. The paucity of cases in this order permits little information to be drawn from the form of tuberculosis. The total seems to have been swollen by a group of three beavers, all of which came in one shipment. The remainder were a Capybara and an Agouti. The general type is that of much caseation with little or no surrounding fibrosis. One illustrative case is cited:

American Beaver (_Castor canadensis_). General tuberculosis. The
animal presents generalized tuberculosis. The regional lymph nodes
show caseous nodules. The right hip joint shows caseous material about
the acetabulum with necrosis and pathological fractures in the os
innominatum immediately above the acetabulum and including its cavity.
Lungs show almost no normal respiratory tissue, the process being a
diffuse precaseous, partly gelatinous pneumonic phthisis. The superior
and posterior mediastina show caseous glands. There is miliary
tuberculosis of the liver. Nodular caseous tuberculosis of the spleen
with small tubercles and some cirrhosis of the intervening tissue.
There are caseous nodules in all perirenal glands and in the kidney
cortices. The psoas muscle glands are densely caseous. The pelvic
organs except about the right acetabulum escape involvement. Adrenals
not opened but probably not involved.

Ungulata. This order shows the most definite figures among those for the order of mammals. Nearly one-tenth of the whole number of specimens have had some form of tuberculosis and of a very definite character. It is well at first to mention, however, that only four of thirteen families are represented, from which four came 328 of the total 365 autopsies. The remaining thirty-seven were such animals as tapirs, giraffes, swine, and peccaries, in all of which tuberculosis has been reported from elsewhere.

Pulmonary disease with less prominent lesions in other organs, especially the intestines and their related glands, speaks in favor of the aerogenic route being the common one. This of course has been a bone of contention among veterinarians, and I do not presume to settle the matter with these figures.

This order resists tuberculosis to a certain degree as attested by the fibroulcerative character of the majority of the cases. Two instances, one in a buffalo and one in a deer, showed very highly fibrotic pulmonary lesions with a partial attempt to surround and wall off numerous areas of caseation. So too in this order there is a greater tendency to calcification, both in the intra- and extrapulmonary nodes. It is to be emphasized that in our material the thoracic lymph nodes are affected more than the abdominal and regional as 3 to 1. The apparent immunity of the spleen of this order is well illustrated.

The paucity of serous surface involvements in the wild Bovidæ and their prominence in the Cervidæ cannot be ignored in the figures, but it seems misleading since pleural growths and adhesions are quite common in the domestic Bovidæ. The case in the Equidæ was that of a Zebra with a large tuberculous abscess in the retroperitoneal glands forming a tumor in the left renal region. It was quite well surrounded by fibrosis, and the infection had not extended; it seemed quite recent. Analysis of the figures for the remaining three families of ungulates offers little for contrast and much for comparison; it is the usual picture as seen in the domestic cow. Some special cases are worthy of review.

An interesting specimen of softened glands chiefly on one side of the neck was found in a Fallow deer (_Cervus dama_). It resembled the juvenile human cases that require surgical attention. Although palpable lymph nodes can be found in practically all cases of generalized tuberculosis in the Ungulata, this is the only case in our records in which they have presented a large tumefaction and broken down. Pulmonary cavitation is recorded but thrice, one for each of the last three families. Fibrocaseous tuberculosis of the testes was discovered in a Nylghaie (_Boselaphus tragocamelus_), but there is no knowledge of mating or offspring. An ischiorectal abscess was found in an American Bison (_Bison bison_) showing nodular precaseous tubercles of the lung. The former was the cause of death. No tubercle bacilli could be found in the abscess contents, so that the tuberculous basis is inferred, not proven. Tuberculous salpingitis in a Nylghaie was discussed on page 306.

Proboscidea. Eber mentions in the article already referred to that there are three reports in the literature of tuberculosis in elephants. When looking for an explanation of tuberculosis in this animal it must be remembered that it is one of the most attractive objects in a zoological garden and receives perhaps more attention, including feeding, from visitors than any other specimen. The beast while possessing some tissue resistance to tuberculosis, is by no means immune thereto, as has been thought by some persons on account of its reputed longevity, and therefore he is to be protected from infection just as much as other animals. It would appear that he may present caseous pneumonia or nodular caseous disseminated lesions. Our two cases, in animals at the Garden twenty and thirty-eight years respectively, were both of the fibrocaseous variety; the lesion was confined to the lungs. A brief description of their lesions is as follows:

Indian Elephant (_Elephas indicus_) ♂ . Chronic polyarthritis. Chronic
myocarditis. Chronic hepatitis (cirrhosis). Parenchymatous nephritis.
Chronic tuberculosis of the lungs, partly encapsulated. Pigmentation
of the spleen. The pleuræ are very fat but the surfaces are smooth and
devoid of adhesions. The lymph nodes of the mediastinum are about
10 × 20 cm. for the largest while the smaller ones vary around 2 × 4
cm. They are firm, deep red-brown without clear divisions into medulla
and follicular cortex. There are several large, firm, pale rather
cheesy follicles in all the large ones and a few of the small. These
do not appear like tuberculosis. The lungs are flaccid and soft; gray
and red mottled. The bronchi are firm and stand open. Around one in
the upper lobe of the right lung, there is a large area of cheesy
degeneration around which a zone of connective tissue has formed. This
extends about the bronchus about halfway in a sheath-like manner.
There is also a separate nodule the size of a cherry with a cheesy
centre. The trachea appears normal. Tubercle bacilli could be
demonstrated in the cheesy material. Microscopic section of lung
around the cheesy area shows a low grade chronic granulation tissue in
some places enclosing cheesy masses with giant cells on the margin.
The neighboring septa are slightly thickened and in some places
broken, forming emphysematous cavities. Some of these cavities are
edematous.

Indian Elephant (_Elephas indicus_) ♀ . Miliary and conglomerate
caseous tuberculosis of lung. Edema of lungs. Endarteritis deformans
of lung. Cloudy swelling of liver. Chronic passive congestion of
liver. Hemosiderin pigmentation of liver. Acute parenchymatous
nephritis. Chronic passive congestion of spleen. Chronic hyaline
perisplenitis. Multiple calcified fibroid tumors of uterus. Leiomyoma
of uterine cornu. Senile atrophy of ovaries. Acute catarrhal
enteritis. There are some adhesions of the upper lobes of the lung to
the ribs. The lungs are large, increased in weight, color pink and
mottled red, air content diminished. There are several masses of
tubercles, each as large as a cocoanut, in both lobes. In one such the
tubercles are yellow and caseous; some are fibroid but none are
liquefied or calcified. The fibrous tissue of the lung parenchyma here
is much overgrown. In one instance the terminus of a bronchus is
solidly plugged by caseous material. Mucosa of bronchi is reddened,
markedly ulcerated, ulcers overlaid by mucopus.

INDIVIDUAL FEATURES OF AVIAN TUBERCULOSIS.

The avian form of tuberculosis is somewhat peculiar in its physical appearance as well as in its distribution. The isolated nodular type is far and away more common by more than 100 per cent. than all the other types combined. These nodules are usually well circumscribed, and to the naked eye suggest that they have a restraining fibroid wall. This is, however, not the case, the impression being due to the dense but actively growing fibrocellular cortical zone of the tubercle. The centre of the nodule, instead of having the soft character like Camembert cheese, resembles the firm but brittle American dairy cheese. Upon opening such an area the central necrotic mass may split away from its cortex and even shell out, leaving a cavity lined by a gray-yellow membrane. These characters are best displayed in nodules of moderate size, the small ones being like the yellow mammalian analogue, the large being like indefinite cheesy masses. In the surrounding tissue evidences of inflammatory processes seem decidedly greater in our material than I am accustomed to see in human and veterinary pathology. This, it seems, should be emphasized since secondary infection with pus cocci and other pathogenic germs appears less often in birds than in mammals.

The difference speaks, therefore for a difference either in the tubercle bacillus of birds or the avian physiology. Judging by the limited morbid processes produced by injecting avian bacilli into rabbits and guinea- pigs the reaction of the bird itself would not seem wholly responsible for the difference. The local tissue reaction in all avian lesions is mononuclear and fibrous, softening and pus being rare. It would seem from this and similar operations that the bird expresses its resistance to the bacteria by a fibrocellular reaction which goes on to fibrosis without softening; perhaps this means also that their polynuclears are not sufficiently active, but the pathogenic power of the bacillus itself doubtless is individualistic.

The character of the cheesy degeneration is likewise different from the mammalian. It seems like an abrupt hyaline necrosis of a large central mass and not the slower cell death seen in the other types of tubercle. At times the degenerated area, instead of having the yellowish color of caseation, will present what we have designated “gelatinous tuberculosis,” the whole infiltrated area resembling boiled sago or tapioca. This seems to be a complete homogeneous coagulation or hyaline necrosis of the whole mass out to the delicate fibrous mantle supplied by the tissue in which the tubercle lies.

The organic distribution of tuberculous lesions has already received some attention and is to be discussed with the orders. There are, however, some localities affected conspicuously in the bird. The skin lesions often attract attention during life. They occur around the eye, at wing joints, on the cresta sterni and on the legs. Parrots and jays have shown nodular or diffuse growths around the eye, originating both in the lids and orbit, which on section have proved to be tuberculous. These seldom ulcerate, but those upon the skin of the breast and wings tend to have superficial erosions or deep ulcers. The latter lesions are more common upon pigeons but have been seen in Psittaci and Galli. Toucans and pigeons when pinioned, have on three occasions shown a tuberculous mass on the stump.

FIG. 52.—MASSIVE TUBERCULOSIS IN LIVER AND SEVERAL MURAL TUBERCLES OF
INTESTINE. COMMON PEA FOWL (PAVO CRISTATA).
]

FIG. 53.—NODULAR HEPATIC LESIONS IN THE LIVER OF A DOVE.
]

Two parrots with hyperkeratosis of the beak and of the skin of the feet, have also had tuberculosis. These have been mentioned in literature as of tuberculous origin. One case well studied failed to show tubercle bacilli in the corns. In the absence of tubercle bacilli, one is inclined to think that this might be explained on the basis of a circulating toxin such as is assumed to be responsible for hypertrophic periosteitis. This latter condition has not been seen in birds.

Still another type of occasional occurrence deserves mention. While most of the lesions in birds correspond to the description given in the preceding pages, some lesions fail to degenerate in the centre, retaining instead a solid homogeneous fleshy character of dull gray- yellow color. Upon section these have been found wholly cellular in construction. To distinguish them from the ordinary nodules they have been designated tuberculomata. Lesions of this kind may occur along the lymphatic paths, indeed seem more common in the lateral cervical and thoracic chain, and upon bones and nerves. When they are numerous the nodular caseous type is inconspicuous. They suggest the bovine infection (Pearl disease), but one attempt to prove this failed. We are of the opinion that this is the avian lymphatic form, as our examples correspond to the literary descriptions of cervical tuberculous lymphatics in birds. No especial variety of bird is more often affected by this process.

Intestinal tuberculosis among the Aves may be said to assume three forms. The best known, indeed the form usually spoken of as representing the common picture, is that which produces varying sized nodules upon the serosa, sometimes associated with adhesions to neighboring intestines. Just how this type develops is not known. In some quarters it is believed to originate by the penetration of the tuberculous granulation tissue from the mucosa through the intestinal wall by following lymphatic channels and that irregular contractions of the musculature squeeze the exudate outward under the serosa. Other observers think that the bacilli are carried _via_ the lymphatics to the superitoneal tissue, there starting the tubercle. The truth of the matter will probably be that both methods are operative although we have seen more cases suggestive of the second than of the first explanation. When these peritoneal nodules are numerous and prominent, mucosal ulcers are uncommon and _vice versa_.

The second form is the ulcerative, flat ragged or crateriform defect situated in a diffusely thickened wall. This was well illustrated in cases of pulmonary infection in doves and guans, suggesting reinfection of the gut tract from swallowed tubercle bacilli or a backward development of the disease after the lungs were nearly solid.

The third form of tuberculous enteritis is quite interesting and striking. It is best seen in the duodenal loop but may occur anywhere. Diffuse thickening of the enteric wall is noted, and when palpation is practiced a resilient but leathery sensation is obtained. Careful inspection reveals the mucous surface to be velvety, a condition due to a swelling, that is widening, of the villi which retain their erect position and, when washed in flowing water, will be seen to move like a field of grain in a breeze. The serosa may be, usually is, negative. Studied microscopically the peculiarity of this form is in the development of tubercles and diffuse cellular exudation in the villus stalk, sometimes extending into the submucosa also. Round cell masses like lymph follicles are sometimes prominent. This form is not associated with any peculiar organic distribution so far as my studies go.

FIG. 54.—TUBERCULOUS MASSES OF INTESTINAL WALL SHOWING OUTWARD GROWTH.
SOMETIMES THESE MASSES OBSTRUCT THE LUMEN.
]

Passeres. The peculiarity of this order seems to be in the predominance of the pulmonary route as origin of tuberculosis. Perhaps in no other order has there been such extensive and advanced lesions as in these little birds. Sometimes one whole lung will be solid while its fellow will be half occupied by caseous material. The doves alone seem to approximate the Passeres in ability to live with so much tuberculous exudate.

Picariæ. Specimens from this order illustrate well the intestinal origin and distribution of tuberculosis. There was, among these birds, one case showing tuberculomata which was, because of its gross anatomy, listed as the pearl type. Its description is as follows: