878 Leukemia of Chickens. 



The boOics resembling protozoa seen by Yutaka Kon were also found by 

 EUermann & Bang, and these also observed in the bone marrow round bodies 

 resembling parasites; the authors, however, refrained from expressing an opinion 

 as to the nature of these bodies. Hirsehfeld & Jacoby, on the other hand, found 

 peculiar long bacilli, which produced a temporary anemia with lymphocytosis in 

 an experiment chicken; still they do not yet desire to consider this bacillus as the 

 cause of the disease. 



Pathogenicity. The disease may be transmitted to chickens 

 by intravenous or intraperitoneal inoculations of affected 

 organs, Avhereas other species of birds, likewise giiinea pigs 

 and rabbits, are not susceptible; subcutaneous injection, on the 

 other hand, is negative even in chickens. After an incubation 

 of 1 to 2 months about 40% of the inoculated chickens become 

 affected, and then about one-half of the birds show indications 

 of leukemia, the other half those of pseudo-leukemia. 



Pathogenesis. The irritation of the virus produces a great 

 increase in the production of white blood cells in the capillaries 

 of the bone marrow, liver and spleen, whereby in these places 

 an accumulation of white blood cells results, especially of large 

 mononuclear cells, and also the appearance of myelocytes. The 

 active production at these places of white blood cells is indicated 

 by extensive mitosis. The tissue of the bone marrow atrophies 

 with the local increase of the white blood cells, while the myeloid 

 tissues of the liver on the contrary increase. Temporarilj'^ 

 the predominating intravascular process remains confined to 

 the blood-forming organs without flooding the blood with white 

 blood cells (according to EUermann leukosis aleukaemica, 

 pseudo-leukemia). In about one-half of the cases, however, the 

 circulating blood becomes flooded with the newly formed white 

 blood cells (according to EUermann & Bang, Leukosis leukae- 

 mica), probably for the reason that there are no aggiutinines 

 present at the places of formation. On the other hand, in some 

 cases a local increase of cells occurs very strikingly in the tissue 

 of the peritoneum (according to Hansen, so-called multiple 

 Sarkomatosis of the peritoneum). Hand in hand with the 

 leukemic process an anemia also develops, either as the result 

 of a check in the formation of red blood cells, or then, owing 

 to an increased destruction of these cells under the action of 

 hemolytic toxins. 



In opposition to the above-described conception of EUermann & Bang, and 

 Hirsehfeld & Jacoby, Skiba maintains on the ground of his observations in 

 chickens which died of other infectious diseases, that on one hand chicken leukemia 

 differs from the similarly named affection of mammals, and that on the other 

 hand it probably represents a disease which is associated only with a marked leuco- 

 eytosis. Chickens are supposed to have in general a great tendency to re^^poud 

 with a marked leucoeytosis to infections, or to other harmful influences (insuffi- 

 cient exercise, improper keeping). The principal difference between leukemia of 

 chickens and that of mammals is supposed to consist in the main, in that in chicken 

 leukemia the tissue proper of the blood forming organs rcTuains unchanged. 

 Schridde maintains further that a disease simulating chicken leukemia may also 

 be produced by intravenous injections of organ emulsions of healthy chickens, 

 which, however, was not substantiated by the experiments of Hirsehfeld & 

 Jacoby. 



