474. ANNUAL REPORT SMITHSONIAN INSTITUTION, 1959 
beings, and wondered why those before him had neglected the obvious 
pig-Ascaris relationship as an experimental tool. By using both the 
human and porcine strains of Ascaris, he inoculated pigs and ascer- 
tained that the hepatic-pulmonary developmental cycle in this host 
was no different from that in rodents. Contrary to his expectations, 
he failed to observe development of Ascaris in the pig’s intestine to 
any significant extent. Stewart was unable to account for the exit 
of the larval worms of the pig Ascaris from its accustomed host only 
a few days after completing the journey through the liver and lungs— 
a behavior not essentially different from that he had seen in rodents. 
He thought of the possibility that either Ascaris might undergo a 
direct development in the intestine, once it had returned there after 
completing the hepatic-pulmonary cycle, or that the rat and mouse 
might be intermediate hosts. 
EXPERIMENTAL DEMONSTRATION OF DEVELOPMENTAL CYCLE IN ANIMALS 
Ransom and Foster (18), whose investigations on the life cycle of 
Ascaris followed on the heels of Stewart’s discoveries in 1916, rejected 
the view that rats and mice were involved in any way in the de- 
velopmental cycle of the pig or human Ascaris. They regarded the 
hepatic-pulmonary migratory cycle as part of the normal develop- 
mental pattern of the worm in a one-host system, even though they 
themselves had had no better success than did Stewart in demon- 
strating a direct development of the helminth in the pig. Asa matter 
of fact, the first entirely convincing experimental proof of a direct 
development of the pig Ascaris was supplied by Ransom and Foster 
in experiments with sheep and goats, two rather unusual hosts for this 
parasite. In an autopsy on a kid 28 days after the first, and 11 days 
after the second inoculation with the swine Ascaris eggs, they found 
numerous larvae in the lungs, trachea, pharynx, esophagus, rumen, 
and abomasum, and larger and more numerous worms in the intestine. 
The worms in the intestine, almost a centimeter long, had developed 
presumably, from the first feeding, 4 weeks earlier, whereas the mi- 
erating larvae had apparently developed from eggs of the second 
feeding, about 214 weeks later. The localization of the larvae in the 
organs aforementioned showed very clearly the path they had trav- 
ersed before reaching the animal’s intestine. From a lamb autopsied 
about 314 months after a similar inoculation with pig Ascaris eggs, 
they recovered from the intestine 50 partially grown worms, 10 to 15 
cm. long. Considering the fact that sheep are rarely affected by the 
swine Ascaris, and that only one worm or a few at most, usually 
stunted in growth, have been observed in these aberrant hosts, the 
presence of 50 worms in a lamb that had been experimentally inocu- 
lated with the eggs may be considered conclusive proof of a direct 
development from the egg to a state approaching maturity. 
