35 
cause and the epizootic now being over, its nature be- 
comes a matter of deduction. The only constant features 
of any importance were the paralysis, the intestinal 
round cell infiltrate and thickening, the pigmentation 
of the liver and the degeneration of skeletal muscles. 
Of the various possibilities, first beri-beri was early con- 
sidered. This is not possible because the food of the 
birds was a varied one and furthermore, none of the nerve 
degenerations of beri-beri were noted. Second, acute 
bacterial or protozoan infections is unlikely because no 
constant primary lesions were discovered at autopsy, 
the numerous cultures failed to reproduce the disease,* 
and other birds living on the stream draining the lake 
were not similarly affected. Third, a food poisoning. 
This is possible first because paralytic symptoms were 
present such as are seen in vetch and mussel poisoning 
and, secondly, because the epizootic ceased when the 
birds were taken from the lake and placed upon the grass. 
If this be the case, the toxic material produced the 
paralysis by direct action on the muscle fibers, just as 
that of typhoid fever does and must also have caused 
haemolysis as shown by the hepatic pigmentation. The 
source of this food poisoning is conjectural. Perhaps 
a dead fish decomposed in the water or there were some 
algae with poisonous properties present. The cause of 
the trouble must be considered undetermined. 
Trichosoma Hepaticum in Prairie Dog 
(Cynomys Ludovicianus) 3605. 
This has, to the writer, been the most promising 
parasitic finding of the year. The parasites are round 
worms of very small size occupying the liver and pro- 
ducing enormous numbers of eggs. In this case the liver 
was distended to ten times the normal size. This 
*NoTE. — It is appreciated that these are not absolute signs, since some infections, such 
as acute articular rheumatism show no primary foci and do not yield bacterial cultures 
fulfilling Koch's postulates. 
