LIFE HISTORY OF ASCARIS LUMBRICOlDES. 



Size of A.scaris Idrnr in (liffcrciit host (iiiiiinil.s. 



21 



In mice. 



In guinea pigs. 



In rabbits. 



Age. 



Location. 



Length. 



Age. 



Location. 



Length. 



Age. 



Location. 



Length. 



Days. 



Liver 



Lungs 



do 



do 



Large intes- 

 tine. 



Lungs 



Small intes- 

 tine. 



Large intes- 

 tine. 



Mm. 

 0. 28-0. 34 

 .34- .4 

 .29- .6 

 . 56- . 86 

 . 38- . 46 



.6-1.12 



.83-1 



.75-1.45 



Dai/s. 

 4 

 5 

 5 

 6 

 6 



6 

 6 



6 

 6 



Lungs 



Pharyn.x 



Mm. 

 0.31-0.45 

 . 3.5- . 83 

 . 5 - . 98 

 . 35- . 69 

 .53- .9 



. 63- . 83 

 .71-1.13 



.9 



.8-1.02 



.65 



Days. 

 3 



o 

 5 

 8 

 S 



8 

 8 



10 

 10 





Mm. 

 0. 19-0. 24 



6 



7 



do 



.23- .45 

 .23- .48 



9 



do 



Trachea 



Esophagus 



Stomach 



Lungs 



.33- .73 



9 



•lO 

 10 



10 



...™lo::::::::: 



do 



Trachea 



Pharynx 



do 



. 75 



.90-1.33 

 .6 



.9-1.8 





Stomach 



1.5 -L 75 









Although there is considerable variation in the size of larvae taken 

 from the same species of animal, from the same organ, the same 

 number of clays after infection, it is evident that there is a general 

 increase in size with the lapse of time and with the progress of the 

 larvae through the liver, lungs, trachea, and into the alimentary 

 tract; and furthermore, although differences in size between the 

 larvae from mice and guinea pigs, respectively, are not conspicuous, 

 there appears to be- a tendency for the larvae 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 larvae from the trachea 

 of a pig that died 7 days after infection. This varied from 0.67 

 to 1.33 mm. in length, 8 of them being more than 1 mm, and the 

 average close to 1.1 mm. These sizes correspond very well to those 

 of larvae 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 larvae 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 larvae 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 larvae 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 larvae 

 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 



