470 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1959 
early attempts in this direction by Richter, Ktichenmeister, Leuckart, 
and others yielded indecisive, or negative, results. Having failed 
to infect a rabbit and a dog after the feeding of the embryonated 
eggs, Leuckart carried out additional experiments with pigs, horses, 
and dogs to which he administered the eggs of their respective 
ascarids. He even swallowed the eggs of A. luwmbricoides repeatedly 
without experiencing symptoms or becoming a host to the worms. 
Leuckart’s tests with animals as well as those carried out by several 
of his contemporaries yielded almost consistently negative results. 
The most significant of the early experiments on the mode of trans- 
mission of A. dwmbricoides was carried out, at Leuckart’s (12) sug- 
gestion, by Mosler in 1860. Having failed on 12 different occasions 
to infect himself or others after the ingestion of the eggs, Mosler 
experimented on several children. They were given gradually in- 
creasing doses of eggs without, however, exhibiting clinical symp- 
toms, except in one or two cases, in which the children became sick 
with pulmonary symptoms accompanied by fever. In the light of 
our present knowledge of the course of infection and early migra- 
tion of Ascaris larvae, these symptoms were certainly suggestive of 
pulmonary ascariasis. 
Another experimental infection was reported by Grassi (7) in a 
German publication issued in 1888. Briefly, in July of 1879, while 
he was professor of anatomy at Catania, Sicily, he swallowed several 
hundred Ascaris eggs containing living and “ripe” embryos. The 
eggs had been collected 9 months earlier from the intestine of a human 
cadaver, and cultured during the intervening period in feces kept 
moist by the addition, from time to time, of several drops of water. 
Thirty-three days later he observed ascarid eggs in his feces, and con- 
tinued to find these eggs consistently for a long time thereafter. As re- 
ported by Grassi (6), his pupil, Calandruccio, also swallowed re- 
peatedly embryonated Ascaris eggs but failed to become infected. 
Calandruccio succeeded, however, in infecting a 7-year-old boy whom 
he freed by anthelmintic medication of the ascarids he already har- 
bored. After assuring himself, by repeated examination of the boy’s 
feces during a period of several weeks, that he no longer passed eggs, 
he gave the lad a capsule containing more than 150 embryonated eggs. 
For the ensuing 20 days all fecal examinations made on this subject 
yielded negative results. These examinations were suspended until 
the 60th day after the inoculum had been given. On that day eggs 
were discovered in the boy’s feces. About a month later, the boy, who 
had shown no symptoms in the meantime, passed spontaneously 143 
ascarids measuring from 18 to 23 cm. long. 
The experiment carried out by Grassi is open to question because 
the 33-day period that intervened between the date of infection and the 
first appearance of eggs in the feces is short by at least 2 weeks or more 
