136 BOARD OF AGRICULTURE. 
head is round, nearly globular, supported by a chitinous bulb 
or capsule, truncated at the end, where the large, round 
mouth is situated. The mouth is surrounded by one to sev- 
eral circles of fine denticles, or converging hooks. The cesc- 
phagus is muscular and thick, club-shaped, separated from 
the intestine by a strong constriction. 
The male is an inch or an inch and a quarter long, with a 
large, membranous, caudal bursa, divided into two lateral 
lobes, which are strengthened by numerous rays; there are 
two long and slender spicules. The female grows to the length 
of one and a half to two inches, with a long, tapering, caudal 
portion, the anus not terminal; the ovaries long and con- 
voluted around the intestines, and showing through the integu- 
ments; the uterine tubes are double and contain great num- 
bers of eggs, in which embryos are developed. 
Alabits. 
This parasite is very common in the horse, generally living 
attached by the hooks of its head to the lining membrane of 
the intestine, particularly in the coecum and colon, but some- 
times in the small intestine and duodenum, and even in the 
pancreas. At the points where it adheres it Figure 83. 
causes small, dark-colored, raised spots. They 
sometimes occur in vast numbers in the large 
intestine, completely covering the surface ; 
the number sometimes amounting, it is said, 
to a million or more. Ordinarily, however, 
these parasites, when lodged in the intestines, 
do not appear to produce any marked dis- 
ease or notable symptoms, although when in 
great numbers, there can be no doubt but 
that they must cause some inflammation and 
pain. More serious results, sometimes proy- 
ing fatal, happen when the worms enter the 
blood-vessels. They produce large aneurisms or dilations of 
the arteries, chiefly in the anterior mesenteric artery, but 
Figure 83.—Selerostoma equinum, female, natural size; and anterior portion en- 
larged; a,mouth; 0, circle of hooks; ¢, esophagus; d, intestine; e, reproductive 
organs. From Cuvier. 
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