Leukemia of the Fowl, v4 
obtained no takes and their strain died out. From a leukemic animal 
given to them by Ellermann and Bang, they transmitted the disease 
into the fifth generation, obtaining both leukemic and pseudoleukemic 
eases. In the blood, they found normoblasts and megaloblasts, i. ¢. 
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 leukemia. 
Burckhardt,” in 1910, advanced the theory, based upon investiga- 
tions of his own on transmissible chicken leukemia, that a particular 
leukeemic virus does not exist, and that in the so-called chicken 
leukemia one is very probably dealing with a very chronic chicken 
tuberculosis. As proof, he claims that with a pure culture from such 
an animal (leukemic) and also with older pure cultures of chicken 
tubercle bacilli, one can produce the same blood picture described by 
Ellermann and Bang for chicken leukemia. The anatomical findings, 
he states, likewise correspond. Gratz” suggested that possibly in 
the culture of chicken tubercle bacilli from the leukemic animal, there 
may have been cultivated, in addition to the tubercle virus, also the 
virus of leukemia. Friedberger™ considered this objection invalid, 
because, as he claimed, one could produce the leukemic blood picture 
also by using old laboratory tubercle cultures. 
Burckhardt,* in 1912, still adheres to his theory, but admits that 
he is unable ever to bring the blood into a leukemic 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 leukemic blood picture. The 
animal, in addition, surely had tuberculosis, because all the transmitted 
leukemic 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 leukemia, until 
finally only tuberculous and not leukemic 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 leukemia, they present the following arguments: (1) The 
blood picture in tuberculosis is never to be confused with that of 
