ROUNDWORM ASCARIS LUMBRICOIDES—SCHWARTZ 471 
for the development of A. duwmbricoides to a state of fertile maturity. 
According to several investigators, the minimum period of the pig 
strain is 49 days, and of the human strain even longer. The results 
of Calandruccio’s experiment on the 7-year-old boy may be accepted 
as valid because the interval between infection and the discovery of 
eggs in the feces was 60 days. Moreover, the worms that the boy 
passed about 3 months after experimental infection were of a size 
corresponding to worms of that age, according to observations I made 
on the growth rate of Ascaris in the pig. 
The successful results reported by Grassi found strong support in 
Lutz’s (15) observations in Brazil on the epidemiology of human as- 
cariasis. Lutz concluded from a study of the environment in which 
Ascaris-infected persons lived that this parasitic infection was in the 
main soilborne, and not, as others before him had supposed, water- 
borne or foodborne. Moreover, Lutz (16) carried out an experiment 
with a human volunteer, aged 82. This individual had been free of 
Ascaris for a period of 20 years, and lived in surroundings where he 
could not possibly acquire this parasite. The volunteer ingested in a 
period of 23 days small numbers of eggs on eight different occasions. 
He experienced rather severe abdominal pain, and also developed a 
bronchitis which probably was associated with the invasion of the 
lungs by Ascaris larvae—a link in the chain which constitutes that de- 
velopmental cycle of the worm that had not yet been discovered at that 
time. He was given anthelmintic medication 28 days after the first 
ingestion of eggs, and passed a total of 85 worms, measuring from 5.5 
to 18 mm. in length. The worms were identified as Ascaris lumbri- 
coides not only by Lutz but also by Leuckart, to whom they were sent. 
Epstein’s experiment, in 1892, with three children, 414 to 6 years 
old, was more convincing than any of the previous attempts to bring 
about an experimental infection with Ascaris. Although the practice 
of subjecting children to medical experiments must be severely con- 
demned, Epstein, by meticulous planning and painstaking observa- 
tions, demonstrated beyond doubt a direct development of Ascaris 
from the embryonated egg to the adult, egg-laying worm in 10 to 12 
weeks. 
It is evident from the foregoing account that early in the last 
decade of the 19th century the basically important facts as regards 
the mode of transmission of A. luwmbricoides had been ascertained. 
It must not be supposed, however, that all investigators accepted the 
idea of a direct development, of the worms in one host up to the 
stage of egg-laying maturity. At first, Leuckart came to the con- 
clusion on the basis of repeated failures by himself and others to 
infect man, the horse, the pig, the dog, and other animals with their 
own or related species of ascarid, that these worms apparently had 
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