Part 36

The skeletal muscles of the wild animals of our collection have been quite free of pathological lesions such as atrophies and dystrophies and indeed seem relatively seldom affected by disease. Occasionally hyalinization will accompany infectious disease or local suppurations will spread into the muscles. Much more often filaria, sarcocystis, flukes and larval insects will be found resident within or between muscle bundles; this will be discussed at a later time. Six tumors have been found, three of which certainly developed in a muscle, while for a fourth case no primary growth was discovered. This last one, to dispose of it at once because of its peculiarity, was an adenocarcinoma found as a firm, conglomerate, encapsulated mass in the sheath of the gluteal muscles of a waltzing mouse (_Mus wagneri rotans_). No other growth was discovered although it must be admitted the body was not exhaustively searched for some tiny nodule to which primary focus this muscle mass could have been secondary. That metastases may be larger than original growths is well known. The gross diagnosis was sarcoma. If this be an original tumor it might be explained as arising from ectopic mammary tissue.

The five other tumors were sarcomata, one of large cells almost syncytial in size, shape and number of nuclei, two definite spindle cell growths and two of fibrosarcoma type. The first occurred in an all green parrakeet (_Brotogerys tirica_), the second in an undulated grass parrakeet (_Melopsittacus undulatus_), the third in a larger Egyptian gerbille (_Gerbillus pyramidum_), the fourth in a white-footed mouse (_Peromyscus leucopus_), and the last in a bean goose (_Anser fabalis_).

SECTION XIII THE CENTRAL NERVOUS SYSTEM AND THE SPECIAL SENSES

Diseases of this system and its specialized end organs of sense in the eye, ear and nose are recognized by veterinarians as occurring among domesticated animals, in which however they are by no means so common as in human beings. Because of the natural reserve of wild beasts and because their habits and manners are not so familiar to the observer, it would seem that clinical evidences of disease of the nervous system are rarest among them. The brain, cord and nerves of our specimens have not been studied with the minuteness accorded to the examination of other viscera since we have not had the personnel to devote the time to this really colossal undertaking, our work with these tissues being directed toward the accumulation and preservation of apparently normal brains from every species; there are now some nine hundred brains on the shelves. However, whenever the history of the animal before death has suggested that disturbance in the nerve organs might exist, they have been dissected grossly and examined microscopically. Had we subjected all our material to microscopic study it is quite possible that we might have discovered more lesions. This is still possible by reason of our gross material and autopsy protocols.

We have been fortunate in having Dr. W. B. Cadwalader, Secretary of the Society, and Dr. J. H. W. Rhein with their broad experience in neurology, take interest in this phase of the subject and study our material. The number of cases in which definite lesions have been found is surprisingly small, so that no generalizations can be attempted except perhaps in a negative sense. After the study of thirty-nine brains and cords from animals in whose history some suggestion of nervous system disease existed, Doctor Cadwalader could find abnormalities in only twenty-two cases, mostly however of a very indefinite character. This observer further points out that in his experience with our material, his observations of our animals and a review of the literature, he is unable to find satisfactory instances of the so-called system or tract diseases such as tabes and lateral sclerosis. This he suggests is due to the absence of arterial sclerosis in the lower types of brain, intimating further that perhaps the relation of syphilis to human arteriosclerosis and degenerative nervous system disease is thereby strengthened. These facts being true it is not astonishing that massive cerebral apoplexy and cerebral softening do not occur[56]. The lesions that have been found were either definitely infectious, as encephalitis or acute septicemia, tuberculosis, poliomyelitis, meningitis, or the minute hemorrhages and vague granularities or vacuolizations of nerve cells in toxemic conditions. The material being limited and broad statements being impossible, the important cases will be cited individually or in small groups.

CONVULSIONS.

Before entering upon the special subjects, a word might be added concerning the clinical evidences of neurologic conditions as seen in the Garden. Perhaps the most common and certainly the most definite clinical sign of nervous disturbance is the convulsion. General spasms or fits are fairly common among the carnivores and monkeys, in the former most often associated with intestinal parasitism, in the latter with no especial relationship unless it be renal disease. The convulsions have been general, with and without the preservation of consciousness. No cases of focal or Jacksonian spasms are recorded although we shall cite two instances of tuberculoma reasonably near the motor area in the cerebrum. The exact cause of many cases cannot be set down since intracranial disease does not often exist.

Intoxication from chemical products of disturbed digestion or from worms themselves is the usual explanation of spasms associated with intestinal parasitism; if this be true, intoxication in the absence of demonstrable parasites may also be the cause in certain cases of enteritis. However we have seen fits when enteritis, parasites and renal disease were not found. If these were true epilepsy, they are instances of perhaps the rarest disease of animals, which I do not presume to diagnose.

Convulsive seizures in herbivorous animals are exceedingly rare although I have seen clonic movements of a spasmodic character in antelopes and deer shortly before death from gastroenteritis. Ataxia and incoördination are much more common. Birds, notably parrots and soft- billed insectivorous varieties, are not uncommonly afflicted with fits but as they are rarely observed except by the keeper the exact nature is difficult to describe. Those seen by the writer have been of two kinds.

The first and more common consists of falling from the perch in a dazed and stiff condition, with dilated fixed eyes, stiffened and spread-out legs and wings. Recovery follows shortly and the bird resumes its perch either in excitement, or slowly and uncertainly, perhaps to have another attack in a few minutes. These cases, in the few instances in which they could be followed, were due to faulty feeding and enteritis and showed either nothing or a mild congestion of the brain. The other variety of fit is epileptiform, a rapidly developing clonic spasm of all parts of the body with a tendency to opisthotonos. In one case of this character, a parrot, no lesions were found in the brain, an enteritis existing however. Another case concerned a pet Indian Shama I had at my home. He had been doing well and singing loudly, until one evening he was allowed to remain in a tobacco-smoke-filled room whereupon next morning he stopped eating and singing. Later that day the clonic form of convulsions appeared, growing worse for thirty-six hours or until death. At autopsy no food was found in the alimentary tract. The brain and cord were congested grossly, while minutely, perivascular hemorrhages and marked vacuolization and diffuseness of staining were found in ganglion cells of the bulb, pons, anterior spinal horns and in the pyramidal cells of the cerebellum. Happening so promptly after exposure to tobacco smoke, when the bird was doing well, I venture to associate the two.

ATAXIA.

Incoördination and ataxia are so often observed and under so many conditions that it is well nigh impossible in any individual case to give an adequate explanation before death. They are in all probability the expression of sickness and nothing more in the vast majority of instances. When they are observed in such cases as the tyromata of the cerebrum or in certain of the ungulates, they may mean something definite. In this latter order and to a less extent in carnivores, one frequently sees weakness and uncertainty of gait in the hind quarters, the legs being usually coördinate but tending to give way under the weight of the body.

From a study of veterinary literature and our own material it would seem that this may have many explanations. In the first place, it may simply indicate weakness expressing itself in the heaviest part of the body, the animal inclining its femora forward to assist in supporting the heavy abdomen. It may be an expression of abdominal pain, the recti becoming rigid and the quadriceps of the thigh participating in the protection of the belly. Almost any of the intra-abdominal conditions, gastroenteritis, mesenteric thrombosis, peritonitis, or diseases of the psoas muscle and lumbar vertebra, might occasion this attempt at support. Disease of gluteal muscles, as hemoglobinuric fever, may produce a palsy of the whole pelvic girdle with weakness of the hind legs. There may be associated with the weakness of the hind legs a humped-up condition of the lumbar spine and retraction of the abdomen, sometimes called “tucked in;” in two definite cases of this last sort we have found renal pelvic stones and once intestinal sand. Some instances are undoubtedly due to meningomyelitis or to poliomyelitis and at the place for this subject a few cases will be discussed. Meningitis has not been found in the ungulates showing this weakness. There have been however cases of ataxia in the hind legs of deer and antelopes, which did not have a ready explanation fitting in with the foregoing. Two of these we thought might be due to certain grasses in the enclosures and have changed the exhibition spaces. No conclusion can be drawn from this as yet. No enterocolic disease could be found nor any lesion of the sciatic nerve and lumbar enlargement of the cord. We have however discovered sciatic neuritis in a case like hemoglobinuric fever in a Burchell’s zebra. The history of the animal is similar to that of this disease in domestic animals in so far as symptomatology is concerned; in so far as confinement in a stall is concerned no data is at hand but death occurred on December 26th in the zebra house whereas he had been accustomed to go out into the yard all summer and autumn.

MENINGITIS.

The coverings of the brain and cord have not been the seat of the well known acute inflammations seen in domestic horses and cattle. Eleven instances of disease in the meninges are recorded but, with very few exceptions, have been accompanied by other lesions offering a ready etiological explanation. These cases are however not very instructive except perhaps three in monkeys where the meningitis seemed to be secondary to gastroenterocolitis. In one case a colon bacillus was apparently responsible, in a second no bacteriology was undertaken and a third was too rotten for the results to be dependable. A focus of infection aside from the intestinal area could not be found. The only noteworthy finding was the scantiness of the cerebrospinal fluid and the almost exclusive subpial exudate; these facts would seem to strengthen the thought that the virus came through the blood stream. Another case was due to extension, through the temporal bone to the lateral sinus, of a necrotizing process beginning in the buccal muscles or parotid gland; the necrosis bacillus and a host of Gram-positive cocci were found. A Canadian porcupine suffered with a mucopurulent nasopharyngitis which involved the deep sinuses, the middle ear and the temporal bone; smears from the pus over the corresponding cerebral hemisphere and from the nasal pus showed pneumococcus forms; the lungs were not affected. The llama which showed the intracapsular fracture of the femur (page 344) had also hemorrhage into a fibrinous exudate in the mastoid cells with deep opaque congestion and edema of the pia above the petrous portion of the temporal bone. Decomposition precluded satisfactory bacteriology but it is suggested that probably injury in falling started a hemorrhage in the ear upon which a secondary infection was implanted. What seems a true meningitis secondary to otitis media and mastoid suppuration was seen in a marmoset.

A case of the well known but obscure condition known as chronic productive pachymeningitis was observed in a badger. Although it cannot be explained it is cited as a matter of record and interest.

American Badger (_Taxidea taxus_). Pachymeningitis externa. The dura is fast to the skull and cannot be removed. Scattered irregularly over the entire inner surface of the skull are pale pinhead sized hard nodules. It is impossible to tell if they are in the dura or the bone. The brain shows engorged vessels but is otherwise negative.

Two instances of hemorrhagic pachymeningitis associated with cretinism were seen in wolf cubs. The following notes illustrate both cases.

American Gray Wolf (_Canis mexicanus_). Cretinism. Hemorrhagic external pachymeningitis with craniotabes. Upon removing the calvarium a marked craniotabes of the under surface is found and with it a deep red and purple staining of outside of dura and inner table of skull. These changes are most marked along the longitudinal sinus at internal occipital protuberance and along left parietal region. Dura on left side is distinctly congested. This is also true of pia. The brain and its base seem normal.

Cyst of the brain. A sooty mangabey (_Cercocebus fuliginosus_) had been in the Garden for about four months and was apparently an adult normal animal. It died rather suddenly after a distinct convulsion with semiconsciousness. At autopsy in addition to a nephritis, a large cyst was found to occupy the posterior third of the left hemisphere. Its walls were composed of a thin (one-sixteenth inch) rim of cerebral substance and the meninges; its contents were clear. The notes do not record any examination for parasites. This monkey showed no localizing signs.

TUBERCULOSIS.

Gross tuberculous lesions have been found in the brain in several specimens with generalized disease but only two cases are of special interest. A Rhesus macaque (_Macacus rhesus_) suffering with generalized but chiefly lymphatic tuberculosis, showed a large plaque on the external surface of the dura over the vertex where it was adherent to a yellow, fairly firm nodule about ten mm. across. This nodule was deeply imbedded in the brain substance, barely projecting above the surface, generally spherical and not encapsulated. There was no peripheral reactive zone. The meninges were not altered anywhere except as above. The blood vessels were not especially congested. The pia arachnoid contained no excess of fluid but the summits of the convolutions were flattened. The mass was located in the posterior frontal convolution, near the longitudinal fissure, occupying nearly its whole breadth and penetrating about one centimetre. It did not enter the fornicate gyrus. There was a completely degenerated core about two mm. across. The adjacent bone was beginning to erode. No localizing signs were reported.

The other case, that of a young Drill baboon (_Papio leucophæus_), was studied with Dr. J. H. W. Rhein and can be reported in the following condensed notes.

The baboon appeared to be perfectly well until October 18, 1906, when some lameness in the anterior and posterior extremities on the right side was observed. This gradually increased, and was associated with general convulsions. On November 30th, I made an examination and found the following condition: The right upper and lower extremities were weaker than on the left side. On the left side the power seemed to be fair. He was able to hold on to an iron bar with the fingers of the upper and lower extremities on the right side but in withdrawing the bar it was not difficult to overcome his grasp and the power on this side was distinctly less than on the left. The movements of the right arm were somewhat ataxic, as observed when he made efforts to grasp the bar. The knee jerks were increased on both sides and appeared to be equally so. There was no evidence of facial palsy. He moved both sides of the face equally well at times when he expressed anger or fear in the facial expression. The tongue seemed to be retracted equally well on both sides. Tests for hemianopsia were, of course, unsatisfactory, but he seemed to recognize readily the approach of the iron bar from both sides. There was no disturbance of the rectal or bladder functions, although at autopsy the bladder was full. Death occurred on December 2, 1906. At the autopsy the brain and spinal cord, with the other organs were examined. The dura was adherent to the left side of the brain, in the prefrontal region, in the upper third and when the brain was removed it was observed that an area of softening lay beneath this point. A small caseous mass was also observed at the base of the right lung, and beneath the diaphragm on the right side was a large abscess, partly involving the liver. The tubercle bacillus was found in the pus removed from the area of softening beneath the left cortex. A study of the brain revealed the presence of three foci of softening. The largest one was situated in the left hemisphere in the prefrontal region, and extended from just beneath the cortex in the upper third of the region, downward almost to the base of the brain. This area was cylindrical in shape and measured 2.5 cm. in its greatest diameter. The area of softening consisted of caseated material and pus, in which the tubercle bacillus was found present. The second area of softening was found on the right side of the brain, much smaller in extent and measuring 1.5 cm. diameter. There was no pus present in this area, but it consisted of a circumscribed mass of caseous material. The apex of this area of softening was just beneath the cortex in the prefrontal region on the right side, and in the removal of the brain the cortex was torn just above this area of caseation. This point was .5 cm. in front of the central fissure and about 1 cm. below the superior surface of the brain. A third area of softening was observed posteriorly, in the white substance, in the parieto-occipital region, and measured about 6 mm. in diameter. A study of the sections of the brain shows beautifully the extent of the destruction of the brain tissue. The optic thalamus and the lenticular nucleus, and the posterior limb of the internal capsule, on the left side, are destroyed in part. The anterior limb of the internal capsule in one section, is preserved, notwithstanding the fact that the optic thalamus on the same side has been in large part destroyed. In spite of the fact that the posterior limb of the internal capsule has been destroyed at some levels, it is interesting to note that the degeneration of the pyramidal tracts of the pons and medulla on the opposite side and the lateral columns of the spinal cord are not intensely—although distinctly—degenerated. It is very interesting to note that in view of the severe damage to the posterior limb of the internal capsule on the left side, there was not more paralysis, for it will be remembered that there was considerable power of prehension in the right upper and lower extremities.

ENCEPHALOMYELITIS, POLIOMYELITIS.

While, as has been stated, no well defined cases of the recognized meningocephalic infectious diseases have been observed in the Garden, there have been several animals in whose cord and brain changes were found comparable to the infections disease known in man as poliomyelitis. On several occasions since this disease was recognized as occurring in epidemic form it has been observed that domestic mammals and fowls suffered from a similar condition. The general vicinity of Philadelphia had a low grade epidemic among children during the years from 1907 to 1912 and it is during this time that most of the cases of a comparable character were observed among our animals. It is to be emphasized that attacks were entirely sporadic and the cases did not appear to bear a relation to one another. This character is quite in accord with certain of the outbreaks in man. However we cannot state that the disease is exactly the same as seen in the human being for, as will be noted in the cited examples, all the pathological features were not fulfilled.

It is not always possible to differentiate between myelitic disease and polyneuritis of man or animals. Studied symptomatically the cases in our records which proved to have degenerative and infiltrative lesions comparable to poliomyelitis showed gradual but progressive paralysis expressed by inability to move rather than disinclination—in other words loss of power rather than restriction because of pain. None of the animals in which poliomyelitis was demonstrated have exhibited the ataxia of the hind legs discussed on a previous page nor have we found myelitic lesions in the few cords from animals suffering with this weakness. The nearest approach to a cerebrospinal explanation for weakness and palsy was in a zebra which died with constipation, acute nephritis, and hepatic perilobular fibrosis. In this animal a pronounced subpial mononuclear infiltrate was observed, in places involving the superficial parts of the cerebral gray matter, especially about the congested vessels of this area. This condition was present to a slight degree in the cord. There was then a low grade meningoencephalitis but no nerve cell changes. So far as is known to me no animal showing a definite local paresis or paraplegia recovered from the attack; had this occurred we might have observed residual palsies.

In so far as lesions are concerned they are perhaps best illustrated by the appended cases, but since even in them there is a lack of uniformity, it may be well to discuss the basic changes of all. The outstanding abnormality in the microscopic anatomy is the richness of small mononuclear cells beneath the pia, both spinal and cerebral, around the smaller blood vessels and to a lesser extent around the multipolar cells of the gray matter. These do not present the dense colonization often seen in the acute cases of infantile paralysis in man but are prominent in comparison to normal nervous tissue. Hemorrhages or at least small groups of erythrocytes outside of blood vessels are seen here and there. Vacuolization of ganglion cells is variable, being prominent in some, trifling or absent in others. Glial proliferation is often quite marked, and in one case to be cited seems the prominent lesion.