Leukaemia of the Fowl. 7 



obtained no takes and their strain died out. From a leukaemic animal 

 given to them by Ellermann and Bang, they transmitted the disease 

 into the fifth generation, obtaining both leuksemic and pseudoleukaemic 

 cases. In the blood, they found normoblasts and megaloblasts, i. e. 

 small and large, round, nucleated, mostly polychromatophilic red blood 

 cells. Although they state that the disease begins in the bone- 

 marrow, they leave it an open question whether in the chicken one 

 is dealing with a myeloid or a lymphoid leukaemia. 



Burckhardt, 15 in 1910, advanced the theory, based upon investiga- 

 tions of his own on transmissible chicken leukaemia, that a particular 

 leuksemic virus does not exist, and that in the so-called chicken 

 leukaemia one is very probably dealing with a very chronic chicken 

 tuberculosis. As proof, he claims that with a pure culture from such 

 an animal (leukaemic) and also with older pure cultures of chicken 

 tubercle bacilli, one can produce the same blood picture described by 

 Ellermann and Bang for chicken leukaemia. The anatomical findings, 

 he states, likewise correspond. Gratz u suggested that possibly in 

 the culture of chicken tubercle bacilli from the leukaemic animal, there 

 may have been cultivated, in addition to the tubercle virus, also the 

 virus of leukaemia. Friedberger 16 considered this objection invalid, 

 because, as he claimed, one could produce the leukaemic blood picture 

 also by using old laboratory tubercle cultures. 



Burckhardt, 1 * in 1912, still adheres to his theory, but admits that 

 he is unable ever to bring the blood into a leukaemic condition by 

 inoculating with tubercle bacilli. 



Hirschfeld and Jacoby" in the same year inform us that they 

 presented to Burckhardt and Friedberger the chicken with which 

 these investigators started their transmissions, and that on the day 

 of delivery it showed a pronounced leukaemic blood picture. The 

 animal, in addition, surely had tuberculosis, because all the transmitted 

 leukaemic animals of the stock from which this animal originated 

 had tuberculosis. They feel confident that in Burckhardt and Fried- 

 berger's stock the tuberculosis had crowded out the leukaemia, until 

 finally only tuberculous and not leukaemic animals were obtained. They 

 had a similar experience with the stock from which Burckhardt and 

 Friedberger's animal originated. 



Against the existence of an etiological relationship between tuber- 

 culosis and leukaemia, they present the following arguments : (1) The 

 blood picture in tuberculosis is never to be confused with that of 



