F. H. Stewart 
219 
and stomach and intestines, heart, lungs and liver were examined. 
No ascarids were found in any of these organs. 
Several factors may have been responsible for this failure: (1) The 
larvae may require to undergo further development either in the outer 
world or in a second intermediate host. (2) The larvae in the lung of 
rat D may have originated only from the first dose of eggs administered 
to it and may therefore have belonged to the Ascaris of man. It is 
of course a point in debate whether the human ascarid (A. lumhricoides 
Lin.) is or is not specifically identical with that of the pig (A. suilla 
Dujardin). Infection experiments only will be able to decide this point. 
(3) The pig B may have been rendered immune to Ascaris infection by 
the large doses of eggs administered to it previously. The eosinophil 
index of the blood was observed to rise after several of these administra¬ 
tions. 
Fig. 1. Larva of Ascaris suilla in the faeces of the rat, 48 hours after evacuation. 
In salt solution, x 340. 
Fig. 2. Larva of Ascaris suilla in the faeces of the rat, 30—40 hours after evacuation. 
The second outline shows the range of movement obseiwed. x 340. 
Description of Larvae found in the Rat and Mouse. 
Absolute and relative measurements of larvae at different stages 
of development. 
To obtain reliable absolute measurements specimens have been 
sketched and measured either in 0'8 % salt solution or in weak corrosive 
subUmate solution. 
Text-figs. 1 and 2 represent larvae passed in the faeces of the rat; 
Fig. 1 forty-eight hours and Fig. 2 thirty to forty hours after evacuation. 
Parasitology ix 
15 
