12 BULLETIN 817, U..S. DEPT. OF AGRICULTURE. 
Stewart (1916a) found larve in the lungs of a mouse within 4 
days after it had been fed Ascaris lumbricoides eggs. We have found 
larve in the lungs of the rabbit and guinea pig as early as 3 days 
_ after feeding Ascaris suum eggs. In rats, mice, guinea pigs, and 
rabbits they may be found commonly in the lungs in large numbers 
from 4 to 6 days after. infection. As they become numerous in the 
lungs they disappear from or become scarce in the liver. In size the 
larve observed by us in the lungs varied in length from 0.2 or 0.3 
mm. (that is, the same as the newly hatched larva), up to 1.8 mm. 
Larve of the latter length have been observed in the lungs of rabbits 
10 days after infection, and slightly smaller in the lungs of a mouse 
13 days after infection. There is considerable variation in the size 
of larve found in the lungs at the same time. For example, larve 
varying in length from 0.29 to 0.6 mm. were observed in the lungs of 
a mouse 7 days after infection; in another mouse from 0.6 to 1.12 
mim. 10 days after infection; in a guinea pig from 0.3 to 0.45 mm. 4 
days after infection; in another guinea pig 0.35 to 0.83 mm. 5 days 
after infection; in another guinea pig 0.63 to 0.93 mm. 6 days after 
infection; in a rabbit from 0.23 to 0.48 mm. 5 days after infection; 
and in another rabbit 0.9 to 1.8 mm. 10 days after infection. We 
have observed that living larve may still be found in the lungs of a 
mouse as late as 23 days after infection, and we have found dead 
larvee encapsulated in the lungs of a rabbit killed 86 days after infec- 
tion, and in the lungs of a pig we have observed degenerated larve 
65 days after infection. 
The larve in the lungs (Stewart, 1916a) enter the air vesicles and 
wander into the trachea. He found them in the bronchi as early 
-as the seventh day and in the trachea as early as the eighth day after 
infection. We have found a Jarva in the trachea of a rabbit 3 
days, and in the trachea of a guinea pig 5 days, after infection. 
They are often numerous in the trachea 6 days after infection. The 
smallest observed in the trachea was 0.23 mm. long (rabbit, 3 days 
after infection). Ina pig 7 days after fection larve were observed 
in the trachea, varying from 0.67 to 1.33 mm. 
From the trachea the larve enter the pharynx. We have recovered 
larvee from the mouth of an experimentally infected animal. 
_ From the pharynx the larve pass down the esophagus. They have 
been observed in the esophagus as early as 6 days after infection 
(guinea pig, rabbit). The latest we have observed them in the 
esophagus has been 10 days after infection (rabbit). No doubt they 
may be found still later. In a pig, 9 days after infection, we have 
observed larve in the esophagus, and there were numerous larve 
in the esophagus of a kid that died 27 days after a first feeding and 
10 days after a second feeding with Ascaris suum eggs. In a mouse 
9 days after infection the larve in the esophagus varied from 0.9 
