6 Harry C. Schmeisser. 



conclude, therefore, that a cell-free filtrate is effective and that the 

 cause must be an organized virus. 



In the same year, Ellermann and Bang 8 reported that the blood of 

 leukaemic fowls contained the virus. They also showed that among 

 transmitted cases the disease may appear as a typical leukemia or as 

 a pseudoleukaemia, or only as an anaemia with changes in the bone- 

 marrow. The injection of five animals with a Berkefeld filtrate re- 

 sulted in one early leukemia. The injected fowls were isolated and 

 great care was exercised during the experiment. 



The following year, 1909, Ellermann and Bang, 10 reported the 

 transmission of the disease into the sixth generation, and also an addi- 

 tional positive Berkefeld filtrate series. Because the disease can be 

 produced by a cell-free filtrate, they conclude: (a) Leukemia must 

 be an infectious disease; (b) it is to be placed among the diseases due 

 to a filterable virus. They call attention to the fact that mitoses in 

 the blood are pathological and always present in leukaemia. 



Schriddle, 11 in 1909, was the first to question whether, in leukaemia, 

 we are really dealing with an infectious etiology. Basing his con- 

 clusions upon experimental work, he claims that chickens, injected 

 with extracts of entirely normal organs, present the same changes 

 as Ellermann and Bang have reported for leukaemia. He thinks that 

 their findings are not leukaemic and that, therefore, there is no proof 

 in favor of the infectious etiology of this disease. 



Hirschfeld and Jacoby 12 in 1909, report a spontaneous case of 

 leukaemia showing changes in the blood and organs which, they claim, 

 agree entirely with the description of Ellermann and Bang. In a 

 second case, the blood picture, although not typical, appeared to 

 them leukaemic. At autopsy this fowl showed a typical chicken tuber- 

 culosis. They succeeded in transmitting this tuberculosis, in asso- 

 ciation with the apparently leukaemic blood picture, into the fourth 

 generation. They did not know whether they were dealing with 

 a combination of tuberculosis and leukaemia in the same animal, or 

 with pure tuberculosis. An animal injected with a pure culture of 

 the chicken tubercle bacillus developed a blood picture identical with 

 that of the second spontaneous case. Therefore it seems highly prob- 

 able that this case may have been one of pure tuberculosis. At any 

 rate, it cannot be accepted as a definite and pure case of leukaemia. 



The following year (1910) the same authors 14 report the injection 

 of fowls subcutaneously from their first spontaneous case. They 



