628 DISEASE IN WILD MAMMALS AND BIRDS 
taneous disappearance and, what is worse, realize that the 
parasitism is likely to become indigenous.- We have sev- 
eral pieces of evidence, however, that the inf estment may 
occasionally quite disappear. Thus, I have seen Coccid- 
ium higeminum spontaneously disappear from a Swift 
Fox (Canis velox) and Spiroptera incerta from a Macaw 
as proven at autopsy. Nicoll(18) remarks that certain 
trematode infestations were hea\ier in newly arrived 
animals than in ones long resident in the Garden. Tliis is 
conceivable on the basis of individual worms dying out, 
i.e., fulfilling their life spans without the host becoming 
reinfested with fresh parasites. Precise information on 
the subject is supplied by Ackert(19) who found that 
cestodes disappeared from chickens in six to eight months 
when the birds were confined, i.e., protected from rein- 
festment. Moreover, it is knowTi that worms can escape 
during acute infections, the infectious state of the economy 
producing conditions obnoxious to the parasite. We hear 
of many instances of their expulsion in human feces and 
vomitus during malaria and the exanthemata of childhood 
and know of similar discharge from animals during the 
death agony. I cite these data largely because they explain 
the scarcity or absence of parasites at autopsy in animals 
which were kno^\^l to have been clinically infested. 
FREQUENCY OF PARASITISM IN WILD ANIMALS 
There can be little doubt that wild animals are more 
frequently infested than man, and furthermore with a 
larger number of parasites. I have no statistical basis 
for these opinions — they rest on personal observations 
of human and animal autopsies, and reports of findings 
in the tropics and elsewhere. They have therefore but the 
value of an indi\'idual opinion. I should estimate rather 
cautiously that "^vild animals are infested at least two or 
three times as frequently as man and much more heavily. 
(18) Proe. Zool. Soc. London, 1914, p. 140. 
(19) Jour. Parasit., June, 1921, Vol. \ai, p. 198. 
