LIFE HISTORY OF ASCARIS LUMBRICOIDES. 11 
feeding Ascaris swum eggs. Apparently they leave the liver more 
rapidly in the case of guinea pigs and rabbits than in the case of 
mice, though this may be only apparent. Given the same number of 
larvee in the small liver of a mouse and in the relatively large liver of 
a guinea pig or rabbit, the presence of larvee in the former case might 
be easily detected, and in the latter only with difficulty or not at all. 
We have actually never seen them in the liver of a guinea pig. Most 
of our guinea pigs, however, were killed or died later than 4 days 
after feeding. Rabbits that were killed or died 8, 10, 86, and 99 days 
after feeding Ascaris suwm eggs showed no larve in the liver. Rab- 
bits killed 3 and 5 days after feeding showed numerous larve in the 
liver, 0.2 to 0.25 mm. long in the first case and 0.23 to 0.45 mm. long 
in the second. 
With reference to the path of migration from the intestine to the 
liver and thence to the lungs, it has been pointed out (Stewart, 1917a, 
p. 227) that there are two apparently possible ways in which the 
larve can get from the intestine to the liver and later to the lungs. 
Assuming that inasmuch asthe thickness of the newly hatched larva 
is three times the diameter of a red blood corpuscle of the mouse, it 
can not pass through the lumen of an ordinary capillary vessel. 
(1) The larva enters a mesenteric venule and is carried to the liver, 
where it is arrested at the entrance to the hepatic capillary plexus. 
‘Acute fatty degeneration of the liver tissue enables the larva to pene- 
trate along the capillaries between the degenerated columns of the 
liver cells to the hepatic venules. The larva then passes in the 
hepatic vein and vena cava to the heart, and by the pulmonary artery 
to the lung. There it is arrested by the pulmonary capillaries. Hem- 
orrhages of the arterioles result and the larva penetrates into the 
air vesicles. (2) The newly hatched larva travels up the bile duct 
and reaches the bile capillaries of the interlobular zone. Working 
its way through the degenerated liver tissue, it reaches a hepatic 
venule and continues its course as in the first case. 
Observations made by the writers are in harmony with the sugges- 
tion that migration from the intestine to the liver may be by way 
of the portal system, and from the heart to the lung by the pul- 
monary artery. Owing to the difficulty of avoiding possible con- 
tamination with larve from other locations than the vessels from 
which the blood was taken in our experiments (Nos. 11 and 12), the 
results of the experiments should not be accepted as in themselves 
sufficient proof of the migration of the larve in the path indicated. 
From general considerations, however, Stewart’s first suggestion 
seems more likely to be correct than the alternative suggestion. As 
noted elsewhere, it is quite probable that some larve migrate along a 
route different from either of those suggested by Stewart. 
