658 DISEASE IN WILD MAMMALS AND BIRDS 
infested cockatoo, showed no ill effects and passed two 
dead female spiroptera and enormous numbers of ova. 
But thereafter it passed even greater numbers of ova 
than before (we estimated 182,000 per day for this bird 
over a five day period and 288,000 on a single subsequent 
day), and was obviously unimproved by the treatment. 
The explanation of failure w^as clear, for the worms can 
retire into the protecting mucus or mucous membrane 
lining the proventricle until the thjTnol has passed by, 
and even though paralysed may not be flushed out. In 
a later test on a toucan which died twenty minutes 
after thymol administration we found at the autopsy 
that worms deeply imbedded in the proventricle were 
translucent and motionless from the effects of the 
thymol-glycerin mixture, i.e., saturated with the medi- 
cament and apparently dead. Twenty minutes later 
they were placed in normal salt solution in the incu- 
bator, and next morning w^ere found actively motile. 
Thymol evidently does not kill — it only stupefies, and in 
the absence of means for flusliing the parasites out, as we 
do in human hookworm cases, this class of vermifuge mil 
have to be abandoned in work against this parasite. 
Not with any serious hope of success, but feeling that 
arsenic was the most promising drug available for 
parenteral use, we tried atoxyl hypodermically and 
arsphenamine intravenously but without success. The 
only positive results were to emphasize the tolerance of 
some lower animals to arsenic. Thus in preliminary work 
pigeons received sixty drops of Fowler's solution by 
mouth without embarrassment, but five minims killed a 
pigeon when administered hypodermically. The organic 
arsenical, arsphenamine, was withstood intravenously by 
pigeons in six times the proportional human dosage. 
One of our drug trials was instructive in that it 
worked quite a different effect from that in man, besides 
being most amusing. In earlier diagnostic work on 
spiroptera we tested the practicability of examining the 
