Pathogenesis, Anatomical Changes. 879 



Therefore the views in regard to the nature of chicken 

 leukemia still differ, and a decided position in this connection 

 is all the more difficult, as the morphologic and biological re- 

 lations of the white blood cells and their part in the different 

 diseases of birds have not yet been investigated sufficiently. 

 The qualitative changes of the white blood cells demonstrated 

 by Ellermann & Bang, Hirschfeld & Jacoby, namely, the ap- 

 pearance of abnormal cells in great numbers, establish very 

 nearly the leukemic nature of the disease. The study of chicken 

 leukemia also opens a prospect for the determination of the 

 nature of leukemia of mammals. 



Anatomical Changes. Most striking is usually the enlarge- 

 ment of the spleen and liver, also the grayish-red discoloration 

 of the bone marrow. However, it occurs not infrequently that 

 the enlargement is insignificant, and the color of the bone 

 marrow does not always deviate noticeably from the normal. 

 Now and then a rupture of the greatly increased spleen or liver, 

 and fatal bleeding in the abdominal cavity is observed. Other- 

 wise fine white points or stripes may be noticed in the liver 

 tissue, even with the naked eye. Histological examination re- 

 veals a considerable increase of the leucocytic, and a diminu- 

 tion of the erythroblastic tissues in the bone marrow, further 

 very marked perivascular leucocytic proliferation in the liver, 

 the capillaries of which appear plugged with leucocytes, while 

 in the spleen numerous pale leucocytes are present and strings 

 may be noticed, formed by capillaries filled with leucocytes 

 which contain small nuclei. In all of these organs numerous 

 cells are undergoing mitosis. Only Eber reports an enlarge- 

 ment of the lymph glands on the neck and in the mesentery, 

 but the diagnosis in that case was not based on blood examina- 

 tion with consideration of the morphological relations of the 

 white blood corpuscles; the autopsy findings are completed by 

 the finding of anemia, while the blood proper manifests the 

 changes to be described below. 



Symptoms. After an incubation of 1 to 2 months indica- 

 tions of anemia become noticeable, inasmuch as the comb ap- 

 pears pale, its turbidity is diminished and the blood obtained 

 by pricking shows a pale red color. In stained blood specimens 

 several small or large, round, nucleated and mostly polychroma- 

 tophilic red blood cells are noted (normoblasts and megalo- 

 blasts). Simultaneously, a relatively large increase of lympho- 

 cytes inay also be observed. At the same time the number of 

 the red blood corpuscles, which under normal conditions, accord- 

 ing to Ellermann & Bang, amount to 3,000,000, according to 

 Skiba however, 6,000,000 per cubic millimeter, gradually dimin- 

 ishes to 1,100,000. Likewise a diminution of the hemoglobin 

 content is noted, inasmuch as the normal value of 50-65° in 

 young chicks, frequently only 40-50° (according to Sahli), drops 



