122 BOARD OF AGRICULTURE. 
then a second constriction separates the stomach or gizzard 
from another somewhat enlarged cavity, which tapers grad 
ually into the slender intestine. The anal orifice is near the 
posterior end of the body, and in the male also gives exit to 
the intromittent organ, which is a single, sharp, grooved 
spiculum, with a very small accessory one. The female 
Figure 79. 
orifice is situated near the anterior third of the body. This, 
like the other species of Oxyuris, produces eggs having firm 
shells. These probably hatch in water, and the embryos may 
thus be swallowed in drinking. The intestines of these para- 
sites are generally filled with vegetable matters derived from 
the food of the animals in which they live, and the structure 
of the digestive organ seems to be adapted to vegetable food. 
For this reason it is probable that they ordinarily cause little 
or no inconvenience to the horses that they inhabit. 
The Pin-worm of Man ( Oxyuris vermicularis Bremser). 
This is a much smaller species than the preceding, but is 
similar inform. Itis very common, often in great numbers, in 
children, and occurs also in adults, especially in aged and 
debilitated persons, and inhabits chiefly the lower part of the 
rectum and the vicinity of the anus. 
The male is about one-eighth of an inch long, with the tail 
curved in a spiral form, terminating in a very short point. 
The female is about four-tenths of an inch long and one- 
fiftieth in diameter, with the posterior part of the body taper- 
ing to a very slender tail. 
The digestive system and structure of the mouth is similar 
to that of the preceding species. But the head sometimes 
shows inflated lateral lobes. 
Reproduction. 
This species is very prolific; each female produces thou- 
Figure 79.----Oxyuris curvulg, female, twice natural size. From Guerin. 
