DISEASES OF BLOOD AND BONE MARROW 105 
posal of Plimmer and his associates, only one ease, a pole- 
cat with lymphatic leucemia, is noted, and but very few 
avian instances. Herewith is submitted the protocol of 
our single mammalian case; perhaps we have missed 
others of a mild grade dying during the early stages 
because their resistance to infection was reduced. 
Unfortunately, perhaps because of the postmortem 
changes, but more likely because it appeared at first as if 
we had to do with a case of generalized tuberculosis, 
the bone marrow in this case was not examined. Never- 
theless the infiltrative character of the lesions, the absence 
of distinct tumors and the numerous mononuclears in the 
blood as seen in sections seem to justify a diagnosis of 
leucemia, in all probability of the lymphatic type. There 
follows this case one with similar gross and microscopic 
picture which has no visible increase of leucocytes, but a 
very distinct myeloid picture in many places. 
Common Opossum {Didelphys virginianus). 6 Adult. No 
evidence of illness. Found dead. Lymphatic leucemia (involv- 
ing all viscera and lymph nodes). Diffuse nephritis. Both lungs have 
become entirely involved in a firm, gray yellow mass not adherent to 
any serous surface. Practically no normal lung tissue is left. This 
seems like tuberculosis but no tubercle bacilli could be found in a good 
smear. Estimation of the normal cubic capacity of an opossum lung 
was made to be about five cubic inches. In this ease not over one-half 
cubic inch remained respirable. Bronchial lymphatic glands were en- 
larged, firm, yellow gray, with no recognizable lymphatic tissue. Heart 
muscle was firm and flaccid, pale and striated. Liver very large, firm 
and tough, with smooth surface and sharp edges. Color pale brown. 
Section surface glistening, dry, smooth, opaque. Common bile duct 
patulous. Spleen, slightly increased, firm, tough consistency, capsule 
smooth. Section surface, smooth, firm, brown-red, pale pulp, prominent 
follicles, andj trabeeulae faintly visible. Right kidney, slightly decreased, 
normal in shape. Capsule smooth, strips with difficulty, tears surface. 
Surface, granular, color brown, consistency firm. Thickness of cortex, 
narrow irregular, markings irregular and obscure. Small mass of 
fibrous material in cortex about 3x3 mm. like those in lungs. There 
are also numerous pale yellow-gray areas in cortex and outer medulla, 
round and streaky, distorting the striated architecture. Right adrenal 
converted to a yellow gray mass like lungs. The mesenteric and retro- 
peritoneal lymph nodes are firm, gray-yellow. This includes those under 
diaphragm and around coeliac axis. 
