364 
T. F. WINCHESTER. 
manner. Railliet has been able to keep them several months 
in this state, or after complete moulting. It is at this period 
that they enter the body of the horse, in the water the ani¬ 
mal drinks (or perhaps on green forage), undergo moulting 
if they have not already done so, and penetrate the substance 
of the mucous membrane. Leuckart asserts that the embryos 
should pass through an intermediate host before entering the 
intestine of the horse. But however this may be, it is possi¬ 
ble that after they have lodged themselves in the mucous, 
membrane, a small number of embryos stay to fix themselves 
in the cysts which they cause to be formed. The majority 
reach the circulatory system, and install themselves in the: 
abdominal arteries—principally at the origin of the great 
mesenteric ; there they form aneurismal dilations, filled with 
a ragged clot that adheres to the inner surface of the vessel, 
and in this helminths are located. 
After an indefinite sojourn in the aneurism, the worms 
leave it by allowing themselves to be carried by the blood, 
and in the course of time reach the csecum, where they form 
the majority, if not the whole, of the submucous cysts. 
Their last migration is, therefore, in reality, centripetal. 
Finally, after remaining a more or less considerable time 
in the tumor they had caused the formation of, and having 
grown, the sclerostomes forsake it, attach themselves to the 
mucous membrane, become sexualized, and copulate. 
An interesting observation of Railliet gives support to this 
theory as to the development, of the sclerostomes. He found 
in a horse a considerable quantity of these worms in the 
caecum, verminous cysts in the walls of that viscus, and a 
smaller number in the duodenum and other parts of the small 
intestine. 
The cysts in the duodenum—which are rare—were grouped 
on the small curvature of the intestine, and some were even 
observed disseminated in the mesentery. All of the latter 
contained sclerostomes still agamous ; but several of those in 
the small intestines, like those of the cascum, had an opening 
in their center and were vacant, the helminths having left 
them. This would seem to prove that the worms had reached 
the intestines by way of the arteries. 
