20 
Leucocytozoon Anatis 
The blood in all cases of infection showed an increase of eosinophiles, 
and the presence of Leucocytozoon anatis. 
Transmission Experiments. Our investigations along this line were 
necessarily limited, as experiments were conducted at the laboratory 
and all the affected ducks died excepting one survivor which was the 
only source from which material was available. 
Young ducks, three weeks old, were inoculated intraperitoneally 
with blood taken directly from the affected individual, and placed in 
a colony house free from infection. Control ducks from the same source 
were employed. A systematic examination of the peripheral circulation 
of these experimental ducks for some days previous to inoculation, 
together with the controls, was conducted. These resulted negatively 
in every instance, no variation from the normal being observed. Subse¬ 
quent to inoculation, these examinations were continued daily and on 
the seventh day two gamete forms were noted in the blood of one of 
the artificially infected ducks. The controls appeared normal. These 
earliest forms appeared as organisms showing a transparent cytoplasm 
containing a few basophilic granules, with a band of chromatin at one 
side but possessing no nucleus. Three days afterwards, the typical 
gamete forms appeared showing the dark blue nucleus. These forms 
persisted for a few days and then suddenly disappeared. No mature 
forms were present in the smears examined at any time during the 
period of observation. White rats were also inoculated, but these 
proved refractory to infection. 
Conclusions. No general conclusions can be drawn until further 
experimental studies are undertaken, but a few salient features may be 
briefly summarized in closing. That the Leucocytozoon above described 
is the causative agent of this disease, we are not prepared to say. The 
fact, however, that this parasite was present in large numbers in all 
affected birds and absent in all the controls coming imder our observa¬ 
tion, is rather significant. Another peculiar feature is the disappearance 
of the mature forms from the blood stream of the affected duck in our 
possession which seemed to coincide with the period of recovery. 
The reason of our failure to transmit the disease may possibly be 
attributable to: (1) The attenuated virulence of the parasite owdng to 
the fact that the disease in this instance was running a chronic course 
and the duck was progressing towards recovery. (2) The fact that 
the disease appears to be prevalent only in the hot months of the year, 
as no fresh outbreaks have occurred at any of the plants under 
observation. (3) The fact that gamete forms appeared in one of the 
