Pathogenesis, Anatomical Clianges. 871 



wliicli have been observed, a differentiation of "Leukaemia 

 lienalis" does not appear justified. 



In view of the fact that in the designation of the forms 

 of leukemia by veterinary authors, the macroscopical changes 

 of the blood-forming organs were almost exclusively taken into 

 consideration, it cannot be decided how frequently the two forms 

 of leukemia occur in animals. In the cases observed by Wolff, 

 de Jong, Nocard, and Hutyra & Marek, the examination of the 

 blood reveals the lymphatic nature of leukemia. In all pro])a- 

 bility the Ijmiphatic form of leukemia occurs in animals much 

 more frequently than the myelogenic form. 



Anatomical Changes. In both forms of leukemia the path- 

 ological changes visible to the naked eye greatly resemble each 

 other. 



The spleen appears considerably enlarged, and excep- 

 tionally its surface is nodulated, its tissue is mostly dense, but 

 at the same time somewhat friable, sometimes, on the contrary, 

 very soft (in dogs and sometimes also in hogs). The cut surface 

 appears usually pale brownish-red resembling the color of rasp- 

 berry jelly, somewhat dry, and with a dull luster, it is not in- 

 frequently permeated by bluish-white, hard or soft, hemp-seed, 

 pea, or up to walnut-sized areas (enlarged follicles), and also 

 by dark red hemorrhages. Sometimes the connective tissue 

 trabeculae form a conspicuous network, and at the same time 

 the capsule is thickened. 



The spleen may at times reach enormous dimensions. Its weight may some- 

 times in horses reaeli 46 kilograms (Cunningham), in hogs 3.7 kilograms (Hel- 

 linger), in dogs 1.7 kilogram (Siedamgrotsky), in cattle np to six times its normal 

 Bize (Mauri). In one case of Zell the spleen had a diameter of 89 centimeters. 

 The cases, however, in which the spleei) is so enormously enlarged were probably 

 in most instances of pseudo-leukemic origin. 



The lymph glands are very frequently enlarged. The 

 glands may attain a size from a hazelnut to a walnut and 

 coalesce with the neighboring glands, forming large nodular 

 bodies. They are either denser or on the contrary softer than 

 normal, their cut surface is uniformly white or grayish-white, 

 in exceptional cases however they are permeated by red points, 

 and a cream-like fluid may be scraped off. 



The bone marrow appears either grayish-red, of jelly-like 

 transparency, softened and entirely filling the marrow cavity, 

 or pale gray and in this case almost of a pus-like consistency. 

 The marrow tissue is changed to a lymphadenoid tissue, which 

 is very rich in white blood corpuscles. Sometimes the bone 

 tissue also becomes rarified and then the spaces appear filled 

 with numerous leucocytes. 



In about half the cases the liver is found to be enlarged, 

 somewhat harder, and on its grayish-brown or grayish-red cut 

 surface pale gray points and a similarly colored network, or 

 hmiphoma-like nodules appear sometimes between the lobules. 



