22 Harry C. Schmeisser. 



it does so very slowly and carefully. Weakness becomes more and more 

 marked, until on the last day it lies prostrated, with its head on the floor, 

 wings drooping, eyes closed and at times is dyspnceic. 



Fever has never been observed. 



Duration of the Disease. This is most frequently from one to two 

 weeks. One case exceptionally acute lasted only 33 hours. Two cases, 

 three days. The longest course was four weeks, four days. 



'Prognosis. Having once begun, the disease progresses steadily to a 

 fatal issue. Only in one case out of 23 leukaemic animals did a spon- 

 taneous cure result. 



BLOOD. 



In Gross. With the onset of anaemia, the vein under the wing col- 

 lapses and the blood undergoes a change. It soon flows with the great- 

 est ease and rapidity, resembles pale yellow water and shows no tendency 

 to clot. The animal apparently would bleed to death from a pin-point 

 wound, if the haemorrhage were not artificially arrested. 



Blood-count. In most cases there is a progressive and extreme de- 

 crease in the total number of red blood cells. At onset the count may 

 be but slightly below normal, 2,224,000, while just before death it, at 

 times, reaches 630,000. More commonly, the lowest point ranges 

 between 1,112,000 and 1,408,000 per c. mm. In one case, the count 

 remained normal. 



The count of white cells is invariably high, between 131,200 and 

 210,000 per c. mm. 



Katioof W/K=l/3-l/9. 



Haemoglobin. This usually falls steadily and reaches a very low 

 point. From slightly below normal, 40-50 per cent at onset, it fre- 

 quently drops to 10-15 per cent just before death. In several cases it 

 fell only to 23 per cent. In one case there was no change at all. 



Blood Smears. The morphology of the leukaemic blood is excep- 

 tionally interesting. In addition to the enormous increase in the num- 

 ber of white cells, all of the cellular elements show marked changes and 

 many new forms make their appearance. Smears were stained by Wil- 

 son's method. 



Classification of blood cells (Fig. 2). 



Erythrocytes. 



1. Normocyte: (a) Normal (a), except for variation in the 

 amount of hemoglobin, (b) Showing anisocytosis, poikilocytosis and 



