ggO Leukemia of Chickens. 



to 15^. During the entire course of tlie disease there exists a 

 hemorrhagic diathesis, as a result of which numerous and fre- 

 quently severe hemorrhages result in some of the patients, and 

 the wounds inflicted on the comb for drawing blood give rise 

 to hemorrhages which are hard to control (Hirschfeld & Jacoby). 

 In this stage the clinical appearance of the disease corresponds 

 to that of pseudo-leukemia. 



As already mentioned the pronounced leukemic picture of 

 the blood appears only in about half of the patients. This fre- 

 quently develops suddenly, and sometimes the birds die quickly, 

 the leukemic changes of the blood being then recogiiized only 

 at autopsy. The increase of white blood corpuscles is usually 

 so pronounced that instead of the normal number of about 

 30,000, 100,000 to 600,000 white blood cells may be counted in 

 the different cases, and the proportion between the white and 

 red blood corpuscles (1:100; according to Skiba 1:250) may 

 fall to 1 :2 or 1 :3. At the same time the percentage of the 

 different cells has changed to such an extent that the large 

 mononuclear cells, instead of the normal percentage of 23, are 

 represented in a percentage of 60-94, wdiile the polynuclear 

 leucocytes and the smaller hanphoc>i;es are forced into the 

 background, and at the same time the granulated polynuclear 

 leucocytes contain spherical granules instead of the usual rod- 

 shaped eosinophilic granules (Hirschfeld & Jacoby). In con- 

 trast to the normal blood round nuclear cells, also with granules, 

 are seen in quite large numbers which maj be considered as 

 myelocytes, and sometimes their granula may attain the size 

 of a ceil nucleus. 



Course. The disease usualh^ lasts only 8 to 14 days, some- 

 times however 1 to 3 months, and unexpected deaths are ap- 

 parently not exceptional. Spontaneous recoveries are very rare 

 (Ellermann & Bang observed such recoveries in two, Hirschfeld 

 & Jacoby in one case). 



Diagnosis. This can be established only on the ground 

 of microscopical examinations, if a leukemic condition of the 

 blood already exists, while otherwise the disease can at best 

 only be indicated by determining the relative increase of hanpho- 

 cytes by the infectious character of the disease, and still more 

 positively by the autopsy findings. The greatest difficulty may 

 be the exclusion of simple leucocytosis, which occurs very fre- 

 quently in chickens and which may at times be very severe. 

 In this the increase of the white blood corpuscles may reach 

 such a degree that the relation of the white blood corpuscles 

 to the red may fall even to 1:26 (Skiba). Leucocytosis occurs 

 especially in chronic infectious diseases of chickens, most 

 noticeably in tuberculosis, and may, as shown by Skiba, pro- 

 duce changes even in the blood-forming organs which resemble 

 those of leukemia. A careful examination of the morphological 



