S. Hadwen 
333 
apparently worked its way upwards, for early in September swellings 
were apparent on the hip and abdomen, and at the end of that month 
a swelling at the lower end of the gullet was indicated by pain when 
swallowing. This moved quickly up the gullet and on October 2nd 
Glaser had the satisfactio)i of extracting a warble maggot, 7-5 mm. 
long, from his own mouth. 
“ This involuntary experiment tends to show that a warble larva 
can bore through the skin of the leg and work its way into the gullet 
in the human subject, and that the insect might pursue the same course 
in the ox. As mentioned in the introduction to this paper, the experi¬ 
ments with muzzled calves tried during several years at Ballyhaise, 
show that animals apparently unable to swallow either the eggs or the 
young larvae of Hypodemia are at the most but partially protected from 
infection. The strong mouth-hooks and piercer and the well developed 
spiny armature of the newly-hatched maggot suggest that it could, 
perhaps, bore as readily through the skin as through the mucous coat 
of the gullet, and we may after all find the former to be the usual 
mode of entrance.” 
The quotation just given supports my belief that the newly-hatched 
larvae penetrate the unbroken skin. 1 have already shown that the 
egg is laid on the legs of the animal and is attached to the base of a 
hair, next the skin. This has been confirmed by Professor Carpenter. 
The parts where the eggs are laid are not easy of access to a cow’s 
tongue and the hair covers the egg completely. Glaser mentions the 
fact that moisture is necessary to keep the larvae alive ; there are many 
opportunities for a cow to wet her legs during a summer day, through 
the dew in the morning or when drinking ; and the skin and hair would 
remain moist for a considerable period. In experiments by Glaser the 
larvae were placed upon an area of shaven skin, but, in Carpenter’s 
abstract of his paper, no mention is made about supplying moisture. 
In any case, an experiment such as Glaser describes places the parasites 
in somewhat abnormal surroundings. The experiments which I shall 
presently describe are also open to criticism, since the larvae had been 
hatched some hours before they were put on the calf, and their vitality 
may have been impaired. 
Several reasons suggest themselves as to why the larvae select the 
gullet in which to pass certain stages of their existence. The areolar 
tissue is only slightly vascular and the reaction on the part of the animal 
against the parasites is inconsiderable. In other organs or tissues 
examples of encysted parasites are frequently seen, but I have not yet 
