Part 4

Taking parasitic infestations by and large, there are close similarities throughout the entire animal kingdom, and the effects produced by a given genus will be repeated almost exactly in several others. The pathological pictures of anemia, of hepatic degeneration, of cystic degeneration, of colonic ulceration or of fibroses are similar in different hosts, only slight variations in the type of inflammation being noted, for instance in reptiles and birds as against the mammals. We have made rather close observations upon the effect of parasites in the production of neoplasms, incited by Fibiger’s discovery of nematodes in the rat’s stomach cancer, but, with the possible exception of a papillomatous growth in the stomach of opossums from the action (?) of physaloptera, we have been unable to establish such an etiological relationship. A decision of the importance of parasites in any given case is not without its difficulty, and we are inclined to reserve judgment pending further analysis unless the effect of the invaders is unequivocal. Leiper[4] does not seem to credit animal parasites with a great effect on the mortality after a specimen has been in the collection six months since all the intestinal varieties he studied came from animals dying in that period. On the other hand the forms which invaded the internal organs and tissues were, in his series, from specimens resident several years in the garden. He seems to think the conditions of life at the garden favor the expulsion of intestinal worms. To what extent some intestinal worms may be commensal remains as uncertain as the value of certain bacteria in the gut tract. In man considerable importance has been ascribed to certain fermentative and putrefactive germs in the maintenance of a reaction unfavorable to strict pathogens and some observers have looked at them as possessing a digestive power. In the digestive tract of the animals eating large quantities of carbohydrate as cellulose, nature provides for its use by rumination and by supplying a large hind-gut, by which means secondary mastication and bacterial decomposition of the cellulose capsule insures its full use. Possibly a similar usefulness may be finally ascribed to some animal microbes or even larger metozoa.

The rôle of vegetable parasites in the causation of disease among wild animals seems as undoubted as it is in the human being and the pathologic results are usually as clear, at least for the entities of which we have exact data, based upon comparisons with man and domestic animals.

There seems to be no essential difference among mammals between the pathological pictures of infectious septicemias, the mucous and serous membrane inflammations and tuberculosis for example. They are characterized by fibrinous, purulent or infiltrative inflammations which may go on to necrosis or repair, by fever, by leucocytosis and by evidences of resistance—all of these things occurring in a similar way throughout the class. Of course not all animals are receptive to all infections since specific racial and generic immunities exist, but the basic response in terms of pathology is similar. There are no normal means of judging the susceptibility of wild animals on their native heath to the important pathogens of civilization, pneumococci, streptococci, staphylococci, cholera bacilli, the typhocolon group, the Friedlander group and others, but it is interesting to note that in captive conditions they evince some receptivity to these germs or their congeners. The pneumococcus takes a fairly heavy toll in zoological collections every year and the Friedlander bacillus, not a very common cause of human pneumonitis, has been seen here and at London.

Among the birds, however, quite distinct differences in some pathological processes occur, not only from the mammals but also within the class. As a whole birds do not produce pus as we know it in man, probably because of the absence from their leucocytes of a protein- splitting ferment; their leucocyte-producing organs do not seem to respond as readily to a virus, the place of purulent exudate being taken by a coagulum or necrosis. The former varies from a clear gelatin-like material seen upon serous surfaces to a thick mat or mass of coarse but short fibrinous strands. Necrosis may succeed upon the latter or occur so promptly as to appear like the original form of degeneration. It is usually rapid, accompanied by a circumferential congestion but not associated with active phagocytosis. Giant cell production is variable, but when developed the appearance is like that of large syncytia. Hemolysis is not marked in the simple infections but a hyperplasia of the mononuclear nodes of the liver is the rule. The function of this nodal increase is not quite clear. It has been always thought that the scanty bone marrow would supply the necessary erythrocytes, but we have seen these mononuclear areas full of pale red cells fitted with round nuclei and without pigment. The fibrin mentioned above does not have the delicate interweaving that we know in a fibrinous exudate in man. This is interesting when we consider the composition of the blood and its coagulation in the Aves. The cell upon which human coagulation seems to depend, the platelet, is represented in birds by the thrombocyte, which appears only up to about 50,000 per cubic millimetre. Coagulation time is relatively short and the resulting clot is firm and irregular. Perhaps this may have something to do with the nature of an inflammatory exudate.

The response to infection on the part of birds may to some extent depend upon differences in anatomy, which are quite distinct, not only from the mammals within which class the anatomy is more uniform, but also from one avian order to another. These differences among the birds may be exemplified by the large foramina between lungs and air sacs in the water birds, a passage which permits infection, notably mycosis, to spread from the first to the second. Again the close apposition of the pancreas to the duodenum over a long stretch permits easy infection of the former from the latter. Still again the large renal-portal vein in the gallinaceous birds explains some of the infections of the liver secondary to intestinal disease. The position of the lungs, deep in the thorax and fitted into recesses made by the sharp anterior border of the ribs and overlaid anteriorly by a rather firm air sac wall, makes it difficult for these organs to expand and therefore renders even a simple congestion a dangerous thing. The position of the ovary subjects the shell-less egg to much danger from the intestinal area.

These and many other peculiarities of anatomy affect the pathological picture in birds. To be sure there are also noteworthy differences among the Mammalia, notably in the intestinal and genital tracts, but the pathologic response is not so varied as in the birds. When due allowance is made for the kind of stomach and absorptive area, apparent differences can be reconciled. For example, there is little confusion experienced in comparing acute erosive gastritis or the follicular enteritis of an omnivorous intestinal tract (man or pig), of a sacculated stomach and absorptive tract (the marsupial), of a carnivorous gut (cat) or a herbivorous compound stomach with its long digestive and water-absorbing surface (cow or camel) and an expansive muscular organ with a very extensive digestive area (seal). The type of lesion seems the same, in that inflammation, pus, necrosis, granulation tissue and cicatrices are comparable throughout the series. The size of the hind-gut has been taken by Metchnikoff as an indicator of the possibility of intoxication by degradation products of digestion. He believes that the capacious colon of herbivora and the short small one in carnivora explain the relatively greater life in the latter, because here less stagnation and absorption can take place. A reference to the expected lengths of life given before hardly substantiates this, and in our later chapters there will be found no strong indication that animals with large colons suffer with degenerative visceral changes more than those with small ones; nay even the reverse may be found true.

In regard to epizoötics the behavior of man and lower animals is similar except perhaps that during an outbreak a smaller percentage of the latter give evidence of individual immunity and whole groups are apt to be carried off. Occasionally hygienic measures stay the ravages, at other times nothing seems to avail. Fortunately it is sometimes possible to sacrifice infective specimens and remove contagion. We have had few serious outbreaks, unless one might call our former heavy infection with tuberculosis in monkeys an epizoötic. The principal ones were an unexplained water fowl disease which carried off one hundred and forty- six birds, an imported epizoötic of quail disease which killed about the same number, a few cases of blackhead among wild turkeys, and a small group of cases of amœbic dysentery in monkeys and of thrush in passerine birds, and a small number of tuberculous pneumonias in snakes.

Pathology may be difficult upon an anatomical basis, but when we engage to explain functional physiological defects we are surely embarked, with a poor compass and weak rudder, upon an uncharted sea. One knows, of course, that all animals require the same amount of food elements per kilo of body weight, that man eliminates his nitrogen as urea and uric acid, that monkeys do the same, that most other mammals destroy uric acid and excrete allantoin, that birds and reptiles form uric acid but chiefly urates, that there is an adaptation of alimentary tract and diet, that herbivores have a high threshold for carbohydrates, that there is a variable quantity of enzyme present in different organs and in different animals, that vitamins, whatever they may be, are necessary for the growth of young animals, that hormones exist whereby correlations of parts are kept normal—but these things, rather than being learned thoroughly from animals, have merely been substantiated by comparisons with man. Constitutional diseases so-called, from which the necessity to investigate much of this physiology originated, are little known in the wild animal. Many cases of so-called gout have been encountered and we have seen an instance of diabetes in a fox, but more extensive experience is needed for definite practical comparisons. This applies to thyroid and pituitary disorders and to the vague conditions we have at times been obliged to call marasmus or inanition.

Some attention has been given to the study of diets for the wild specimens of our Garden, but no systematic observations have been made or records kept upon purely physiological subjects. Reference will be made at appropriate places to accepted comparative physiological facts, but our statistics permit additions to such knowledge only in a limited manner and in isolated instances. Doctor Corson-White has very ably summarized the diet, alimentary tract and physiology of the zoological groups with the pathology as found in our records.

A word might be added here as to the destruction of animals by injury from fighting and harassment by others in the cage. Fighting doubtless causes death, especially when males are together, but it is our experience that in cases of traumatic death search should always be made to see if the resistance of the dead animal had not been reduced by some disease. This is well illustrated in birds. Very frequently a specimen will come to autopsy with its head feathers plucked out, or with a billthrust in the wing or pelvic region. Such birds are not infrequently suffering from malaria, or heavy intestinal parasitism or from organic disease whereby the resistance and self-preservatory power has been decreased.

The foregoing survey of the approach to our subject reveals the multiplicity of factors which affect the study of comparative pathology. No one of them can be entirely omitted, no one is without some effect upon the origin and expression of disease, and no one is fully understood. Yet it is to be hoped that a study of our material, accumulated under routine conditions and uninfluenced by any experimental procedures, will demonstrate the natural response of various zoological groups to morbific agencies. Perhaps reactively some of the modifying conditions may thus be understood. It is also not unreasonable to expect that alterations observed as natural responses in a large number of specimens in nearly normal surroundings would serve as more reliable guides to investigative speculation than would changes in a few animals under artificial technical experimentation. We hope that the few facts we have been able to record may afford someone a basis for further biological studies. It is also to be hoped that something has been learned which in the end will afford an explanation of the diseases of man. Too great optimism in this direction should be guarded against because the human being is indeed an animal _sui generis_ and, from the standpoint of normal conditions of nature, a wild animal.

The zoological classification found on pages 43–46 was compiled in 1903 by Dr. A. E. Brown on the basis of the British System. With a few exceptions the computations in the text are made on the basis of zoological _orders_ since the number of specimens in families is often too small and the complications of so many different figures would be confusing. The tables will be found to correspond to the sequence of the classification. Dr. Corson-White has, however, used for her analysis the dietary groupings. A carnivore in her chapter implies strictly a meat- eater, in the rest of the book one of the zoological group Carnivora.

The Laboratory of Comparative Pathology at this Garden speaks for the earnest desire on the part of the Directors to use the material to its fullest extent, and I, acting for myself and my associates, wish to record our appreciation of the facilities offered to us for study, and for the broad-minded, scientific coöperation the Board has always displayed. The President, Charles B. Penrose, M.D., Ph.D., LL.D., was the active originator of the plan whereby this department was started, and he has given to it continuously the support of his rich experience. I wish to express for myself the deepest appreciation of his personal interest in my studies, and assistance which has been constructive and stimulating. Whether or not this present work prove useful to the extent that is hoped, the results from the Laboratory are such as to make the scientific world debtor to this gentleman.

It is a duty, and a pleasant one, to record, though unfortunately in memoriam, my association with Arthur Erwin Brown, A.M., Sc.D., Ph.D., C.M.L.Z.S., for many years the Secretary of the Society and Executive Officer of the Garden. Doctor Brown as teacher was ever ready to help in the broad subject of biology, and I am proud to recall that he guided me also as a friend.

The first director of the Laboratory was Courtland Y. White, A.M., M.D., who served from 1901 to 1906, retiring then to accept a position in the City Laboratory. The foundation of the recording system is still in use essentially unchanged from his plan, and is a credit to his foresight. Our clerk and technician, Miss Harriet M. Phelps, has served the Garden faithfully and well since 1906. The condition of the museum is very much due to her interest and watchfulness. Thanks and appreciation for her work are felt by every one, the author most of all. Dr. F. D. Weidman has been our first assistant since 1911, and his work on parasitology has been of the greatest value, practically and scientifically. It is to be hoped that we shall be able to retain him indefinitely. Dr. E. P. Corson-White has in recent years taken an assistant position with us, armed for the work with a thorough knowledge of applied organic chemistry and immunology, and has already obtained useful results.

ZOOLOGICAL CLASSIFICATION │

MAMMALIA

PLACENTALIA

PRIMATES

_Simiadæ_ Anthropoid apes

_Cercopithecidæ_ Old World monkeys (macaques, baboons).

_Cebidæ_ New World monkeys (capuchins, howlers, spiders).

_Hapalidæ_ New World monkeys (marmosets).

LEMURES

_Lemuridæ_ Lemurs, Loris, Galagos.

CARNIVORA

_Felidæ_ Cats

_Viverridæ_ Civets, Genets, Paradoxures, Ichneumons.

_Hyænidæ_ Hyena.

_Canidæ_ Dogs, Wolves, Foxes, Jackalls, Etc.

_Mustelidæ_ Marten, Skunk, Weasel, Otter, Badger, Etc.

_Procyonidæ_ Raccoon, Bassaris, Coati, Kinkajou.

_Ursidæ_ Bear.

_Otariidæ_ Eared Seal, Sea Lion.│These are grouped │separately as suborder, │PINNIPEDIA, illustrating │water carnivores.

_Phocidæ_ Common Seal, Walrus. │ „

INSECTIVORA

_Tenrecidæ_ Tenrec.

_Solenodontidæ_ Solenodon.

_Talpidæ_ Moles, Shrews.

_Erinaceidæ_ Hedgehog.

CHIROPTERA

_Pteropodidæ_ Fruit Bats, “flying foxes.”

_Vespertilionidæ_ Common bats.

_Emballonuridæ_ Snouty Bats, Free-tailed Bats.

RODENTIA

_Sciuridæ_ Squirrels, Spermophiles, Marmots.

_Castoridæ_ Beaver.

_Muridæ_ Rats, Mice.

_Geomyidæ_ Pouched Rats, “Gophers.”

_Dipodidæ_ Jumping Mice, Jerboas.

_Heteromyidæ_ Kangaroo Rats.

_Octodontidæ_ Capromys, Coypu.

_Hystricidæ_ Porcupines.

_Chinchillidæ_ Viscacha, Chinchilla.

_Dasyproctidæ_ Agouti, Spotted Cavy.

_Caviidæ_ Guinea-pig, Capybara.

_Leporidæ_ Rabbits, Hare.

PROBOSCIDEA Elephant.

HYDRACOIDEA Cape Hyrax.

UNGULATA

PERISSODACTYLA (odd toed)

_Rhinocerotidæ_ Rhinoceros.

_Tapiridæ_ Tapir.

_Equidæ_ Horse, Ass.

ARTIODACTYLA (even toed)

_Bovidæ_ Oxen, Antelopes, Sheep, Goats.

_Cervidæ_ Deer, Moose, Elk.

_Antilocapridæ_ Prong-horned Antelope.

_Giraffidæ_ Giraffe.

_Tragulidæ_ Chevrotains, Muis Deer.

_Camelidæ_ Camels, Llama.

_Hippopotamidæ_ Hippopotamus.

_Suidæ_ Swine, Warthogs.

_Tayassuidæ_ Peccaries.

SIRENIA Sea-cow, Manatee, Durong.

CETACEA Whales, Porpoises.

EDENTATA

_Bradypodidæ_ Sloths.

_Dasypodidæ_ Armadillo.

_Myrmecophagidæ_ Anteaters.

MARSUPIALIA

MARSUPIALIA

_Didelphyidæ_ Opossums.

_Dasyuridæ_ Dasyures, Tasmanian “Devils.”

_Peramelidæ_ Bandicoots.

_Phascolomyidæ_ Wombat.

_Phalangeridæ_ Phalangers.

_Macropodidæ_ Kangaroo, Wallabies.

MONOTREMATA

MONOTREMATA

_Echidnidæ_ Echidna, Ornithorhynchus.

AVES

PASSERES

_Turdidæ_ Thrushes, Robins, Etc.

_Sylviidæ_ Warblers, Kinglets.

_Paridæ_ Titmouse.

_Troglodytidæ_ Wrens, Mockingbirds, Catbird, Etc.

_Pycnonotidæ_ Bulbul.

_Crateropodidæ_ Babblers, Jay-thrushes.

_Oriolidæ_ Oriole.

_Motacillidæ_ Wagtails.

_Dicruridæ_ Drongos.

_Mniotiltidæ_ Chats, Warblers, “Woodwarblers,” Etc.

_Cœrebidæ_ Sugarbirds.

_Vireonidæ_ Vireos.

_Laniidæ_ Shrikes.

_Ampelidæ_ Waxwing.

_Hirundinidæ_ Martins, Swallows.

_Meliphagidæ_ Honeyeaters.

_Tanagridæ_ Tanagers.

_Ploceidæ_ Weavers, Whydah birds, Waxbills, Finches, Etc.

_Fringillidæ_ Finches, Sparrows, Buntings, Grosbeaks, Etc.

_Icteridæ_ Hangnests, Troupials, Grackles, “Blackbird,” Etc.

_Sturnidæ_ Starlings, Mynahs.

_Corvidæ_ Crows, Jays, Magpies, Jackdaws.

_Alaudidæ_ Larks.

_Tyrannidæ_ Tyrans.

_Cotingidæ_ Bellbird, Cock-of-the-rock, Etc.

PICARIÆ

_Upupæ_ Hoopæ.

_Trochilidæ_ Hummingbirds.

_Cypselidæ_ Swifts, “Chimney Swallow.”

_Caprimulgidæ_ Night hawk, Whip-poor-will.

_Coraciidæ_ Roller.

HALCYONES

_Alcedinidæ_ Kingfisher.

_Momotidæ_ Motmots.

BUCEROTES

_Bucerotidæ_ Hornbill.

TROGONES

_Trogonidæ_ Trogons.

SCANSORES

_Picidæ_ Woodpeckers.

_Rhamphastidæ_ Toucans.

_Capitonidæ_ Barbets.

COCCYGES

_Cuculidæ_ Cuckoos.

_Musophagidæ_ Touracous.

PSITTACI

_Loriidæ_ Lories, Lorikeets.

_Cacatuidæ_ Cockatoos.

_Psittacidæ_ Macaws, Conures, Amazons, Parrots, Parrakeets.

STRIGES

_Strigidæ_ Barn owl.

_Bubonidæ_ All other owls.

ACCIPITRES

_Falconidæ_ Buzzards, Hawks, Falcons, Eagles, Etc.

_Serpentaridæ_ Secretary Vulture.

_Catharidæ_ Vultures.

COLUMBÆ

_Treronidæ_ Fruit pigeons.

_Columbidæ_ All other pigeons and doves.

PTEROCLETES

_Pteroclidæ_ Sand grouse.

GALLI

_Tetraonidæ_ Grouse, Ptarmigans.

_Phasianidæ_ Pheasants, Fowls, Turkeys, Quail, Etc.

_Cracidæ_ Curassows, Guans, Etc.

_Megapodidæ_ Brush turkey.

HEMIPODII

_Turnicidæ_ Hemipodes.

FULICARIÆ

_Rallidæ_ Rails, Porphyrios, Gallinules, Coots, Etc.

ALECTORIDES

_Aramidæ_ Courlan.

_Eurypygidæ_ Sun bittern.

_Gruidæ_ Cranes.

_Cariamidæ_ Cariama “Crane.”

_Psophiidæ_ Trumpeters.

LIMICOLÆ

_œdicnomidæ_ Thicknees.

_Charadriidæ_ Plovers, Sandpipers, Curlews, Woodcocks, Etc.

_Chionidæ_ Sheathbills.

GAVIÆ

_Lariidæ_ Gulls, Terns.

_Stercorariidæ_ Jaeger Gull.

PYGOPODES

_Colymbidæ_ Loons, Grebs.

_Alcidæ_ Auks, Murrs, Puffins.

IMPENNES

_Spheniscidæ_ Penguins.

STEGANOPODES

_Sulidæ_ Gannets.

_Pelicanidæ_ Pelicans.

_Phalacrocoracidæ_ Cormorants.

_Anhingidæ_ Darter “Water turkeys.”

TUBINARES

_Procellariidæ_ Petrels, Fulmars.

HERODIONES

_Ardeidæ_ Herons, Bitterns, Egrets.

_Ciconiidæ_ Storks, Ibises.

_Plataleiidæ_ Spoonbills.

ODONTOGLOSSÆ

_Phœnicopteridæ_ Flamingoes.

PALAMEDEÆ

_Palamedeidæ_ Screamers.

ANSERES

_Anatidæ_ Swans, Geese, Ducks.

STRUTHIONES

_Apterygidæ_ Kiwis, Apteryx.

_Casuariidæ_ Cassowaries.

_Struthionidæ_ Ostriches.

_Rheidæ_ Rheas.

CRYPTURI

_Tinamidæ_ Tinamous.

_List of Animals subjected to Autopsy giving the number of each. These Figures are used to obtain the percentages quoted in the Tables and Text._

MAMMALIA Primates 498 Lemures 86 Carnivora 481 Pinnipedia 20 Insectivora 6 Chiroptera 5 Rodentia 198 Ungulata 365 Proboscidea 3 Hyracoidea 7 Edentata 16 Marsupialia 175 Monotremata 0 1860 ————