LIFE-HISTORY OF ASCARIS LUMBRICOIDES. 21 
Size of Ascaris larve in different host animals. 
In mice. | In guinea pigs. In rabbits, 
Age. Location. | Length. Age, Location. Length. Age. Location. | Length. 
BS ae Sa ele aI See Naertesemmrenae ct Sie ae 
Days. | Mm. Days. Mm. Days.| _. Mm. 
f|| Why@esoocceec 0. 28-0. 34 4 | Lungs......-- 0.31-0. 45 a IBN @roosobecc: 0. 19-0. 24 
6 | Lungs........ - 34-4 Oe|acews (oshodoods 135-283 || = 5 feo... Glogs BASE c -23- .45 
U Bose’ Deen BAO -29- .6 5 | Pharynx..-..-.- ' 5 —.98 Op Pao uMes sae -23- .48 
Quire dovtess-c2 - 56- . 86 6 yeunes BA eerS .35- . 69 Slee Sass (0 Ko eaicieatt .33- .73 
9 | Large intes- -38= .46 || ~ 6 |e... Ove ace .53- .9 8 | Trachea.--..... 5) 
tine 
10) || ungss-s-- -2- -6 -1.12 Cees eae Gotts. aisss . 63- . 83 8 | Esophagus... -- . 99-1. 33 
10 oma 1 intes- . 83-1 6 | Trachea... ---- .71-1.13 8 | Stomach -.-.-.- 6 
ine. } 
10 | Large intes- . 75-1. 45 6 | Pharynx...--.- .9 10 | Lungs.....- ies 9,-1.8 
tine. Gilesace dors 22-2. . 8 -1. 02 10 | Stomach. ../s.} °° 1.5 -1.75 
! Z| lun ese se ee . 65 ed 
Although there is considerable variation in the size of larvee taken 
from the same species of animal, from the same organ, the same 
number of days after infection, it is evident that there is a general 
increase in size with the lapse of time and with the progress of the 
larve through the liver, lungs, trachea, and into the alimentary 
tract; and furthermore, although differences in size between the 
larve from mice and guinea pigs, respectively, are not conspicuous, 
there appears to be a tendency for the larve to grow to a larger 
size In a corresponding time in rabbits than in either mice or guinea 
pigs. They seem to grow still larger in pigs in the same length 
of time. Measurements were made of 13 larve from the trachea 
of a pig that died 7 days after infection. This varied from 0.67 
to 1.83 mm. in length, 8 of them being more than 1 mm. and the 
average close to 1.1mm. These sizes correspond very well to those 
of larve taken from the esophagus of a rabbit 8 days after infec- 
tion. The data that have been obtained as to the sizes reached by 
Ascaris larve in different species of host animals in a given period 
of time after infection are not sufficient to allow definite conclusions 
to be drawn, but the larvee seem to grow more rapidly and to a 
larger size during their migrations in large animals than in small 
ones. 
LESIONS ASSOCIATED WITH MIGRATING LARV. 
The principal organs that show pathological changes as a result 
of the invasion of Ascaris larve are the liver and lungs. 
In the liver there is at first a capillary congestion, and hemor- 
rhage by diapedesis; sometimes petechial or ecchymotic areas of 
inflammation are evident on the surface of the liver which later may 
become focal areas of necrosis. Commonly, however, as the larve 
leave the liver the congestion subsides. In our’ most severe cases,. 
such as in the experiment. (No. 23) on the kid, the inflammation 
was very extensive, the liver engorged with blood, bleeding freely 
