Only a small number of primary intracranial neoplasms have been observed in mammals and birds. Either they do not occur as frequently in lower animals as they do in man or they are overlooked. The latter is a probable explanation, as only a small number of animals that die of natural causes come to necropsy and because of the difficulty of opening the cranium with inadequate equipment this part of the examination generally is omitted.
Slye, Holmes and Wells, in 1931, reviewed the literature on intracranial and cord tumors of lower animals and found only 36 cases reported. Twenty-six of these were intracranial tumors, 11 of which were in the hypophysis. They at that time reported 4 new cases of primary intracranial neoplasms, 3 occurring in mice of the Slye stock and one in a green parrakeet (Agatornis pullaria). The neoplasms found in the mice were: an endothelioma of a cerebral peduncle, a papillomatous growth in the ependyma of the lateral ventricle, and an infiltrating adenoma of the hypophysis. The tumor observed in the parrakeet was an adenoma in the hypophysis. In their summary these writers mention that it is especially noteworthy that only one seemingly conclusive report of a cerebral glioma in an animal could be found. Dawes, in 1930, reported two intracranial neoplasms in dogs. One was an ependymal glioma in the right lateral lobe of the cerebellum; the other was described as a small, reddish brown tumor in the left and central lobes of the cerebellum, adjacent to the roots of the seventh and eighth cervical nerves. Feldman, in his monograph on neoplasms of domesticated animals, mentions no new cases. Because of this seemingly infrequent occurrence of intracranial neoplasms in lower animals, the following cases are reported, one a cerebral glioma in a dog, and the other a pinealoma in a silver fox (Vulpes fulvus).
Submitted for publication March 13, 1935.