466 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1959 
many live in the Western Hemisphere. The others are located mainly 
in Africa. The Ascaris-infected persons in the Americas are largely 
confined to Middle and South America. Those resident in North 
America constitute only about 6.5 percent of the affected persons in 
the Western Hemisphere. 
That Ascaris was frequently seen in Europe in previous centuries, 
despite its concealed habitat in the small intestine, was due to its mi- 
gratory habits, especially during fever, coupled with its conspicuous 
size. Its natural passage at times from the alimentary canal, and its 
expulsion following anthelmintic medication, a practice to which 
physicians had to resort very often in those days, made the worm a 
rather familiar object to doctors and patients alike. The spontaneous 
passage of Ascaris from the body was observed in outbreaks of plague, 
cholera, dysentery, typhoid, typhus, and other febrile diseases. Its 
spontaneous exit from the body in the early stages of typhus was re- 
garded as a more or less grave prognostic sign. 
Ascaris has been observed to pass out not only through the anal 
opening, but also through the mouth and nostrils, and sometimes 
through the ears. In fact, the older medical and parasitological lt- 
erature, and that emanating from tropical countries to this day, con- 
tain harrowing accounts of intestinal obstruction by these worms, 
their occurrence as adults in the peritoneal cavity, the vomiting of 
them by children, and, occasionally, the strangulation of youngsters 
by the worms getting into the trachea and bronchi. In the course 
of a few days or weeks, as many as dozens, or even hundreds, of 
worms were reported to have passed out through various openings, 
while others that remained behind were recovered later after anthel- 
mintic medication. No wonder, therefore, that Ascaris, along with 
other intestinal worms, was regarded during the centuries when there 
were practically no barriers to its unrestricted propagation and trans- 
mission from one human host to another, as the cause of severe illness 
and death. As a matter of fact, all the then known intestinal para- 
sites of man were considered to be incitants of practically all diseases 
for which no other cause was apparent. 
Some of the helminths that parasitize man have a more or less re- 
stricted geographical distribution, conditioned by such factors as 
availability of intermediate hosts, and the hosts’ dietary and other 
habits, as well as temperature, humidity, and other environmental 
factors. Others have a less restricted distribution and occur wherever 
their hosts exist. There is no helminth, however, that has a wider 
distribution the world over than A. lwmbricoides. Its extracorporeal 
existence apparently encounters no external environment so utterly 
defeating and no climate so extreme as to check altogether its unre- 
lenting push from host to host. 
