ROUNDWORM ASCARIS LUMBRICOIDES—SCHWARTZ 473 
symptoms following inoculation with Ascaris eggs, and a similar ex- 
periment by Lutz (16) in Brazil. 
Having failed in 1915 to infect two young pigs with the embryo- 
nated eggs of the human and swine Ascaris, Stewart turned his 
attention in 1916 to Davaine’s approach to the solution of the Ascaris 
life history, by experimenting with rats and mice. He inoculated 
rats, using in succession the eggs derived from the human and pig 
hosts on the same test animals. Less than 24 hours later live larvae 
were found in the feces of the rats, and continued to appear there 
for some days. The larvae moved in a languid manner, and were still 
alive 3 days later, after having been kept at a temperature of 25° to 
30° C. On autopsying one of the rats which died 6 days after the 
first inoculation, while the companion rats involved in this experiment 
were showing symptoms of pneumonia, Stewart discovered that the 
larvae evidently had made their way to the liver and Jungs, but were 
not present in the alimentary canal, spleen, or kidneys. Another rat, 
killed 10 days after the first inoculation, contained many larvae in the 
lungs, but none in any of the other organs examined. One of the 
surviving rats which had completely recovered 12 days after exposure 
was autopsied 4 days later. The host had freed itself entirely of 
larvae, so far as could be determined by the examination of the various 
organs in the abdominal and thoracic cavities. Stewart repeated these 
experiments with other rats and a mouse and obtained similar results. 
He concluded, therefore, that in the intestine of rats and mice only a 
few of the larvae that escaped from the egg shells were eliminated to 
the outside, but that most of them were carried to the liver (pl. 2, fig. 
1) and lungs (pl. 2, fig. 2) by the circulation, became localized in the 
respiratory tract for a time, and produced symptoms of pneumonia. 
Curiously enough, Stewart was inclined at first to the view that the 
larvae which left the host shortly after they had escaped from the 
egg shells, rather than those that invaded the tissues, might be the 
starting point of human infections by being transferred to the mouth 
with food or water that had become contaminated with the feces of 
infected rats or mice, 
After confirming and extending his early experiments, Stewart 
traced the migratory path of the larvae through the bloodstream from 
the intestine to the liver and thence to the lungs. He determined 
that by upward migration in the respiratory tract, the larvae reached 
the trachea, pharynx, and buccal cavity, and were then swallowed for 
the second time. Now they migrated downward through the esopha- 
gus to the stomach and intestines, and tended to accumulate in the 
cecum. They finally passed out with the feces 10 or 12 days after 
inoculation. 
Stewart next turned his attention from experiments with rodents 
to experiments with pigs. He objected to experimenting with human 
