120 BOARD OP AGRICULTURE. 



It is therefore probable that they are taken into the 

 human system in impure water. In some regions it is very 

 common. Davaine estimates that one-half of the inhabitants 

 of Paris entertain this parasite. Its effects are not well made 

 out, but it does not seem to cause, ordinarily, any marked in- 

 convenience. It lives in the coecum and small intestine. 

 Trichocephalus affinis Rud. 



This species lives in the coecum of cattle, sheep, deer, and 

 antelopes. It closely resembles the preceding, but the neck 

 part is still longer and more slender. The posterior end of 

 the male is curved in a close, conical spiral, and the spicule, 

 like its sheath, is much longer, being equal to about a third of 

 the length of the body. The genital orifice of the female is 

 situated at the summit of a prominent, hour-glass shaped 

 papilla, which is obliquely truncated at the summit and 

 covered with minute spinules, like those of the spicule-sheath 

 in the male. The eggs are similar to those of the preceding 

 species and, without doubt, develop in the same way. It is 

 not known to cause any serious disease. 



Spiroplera strongylina ^u^., from the Hog". Figure 78. 



The genus Spiroptera includes numerous species of small, 

 whitish or reddish,, slender, round worms, which taper some- 

 what toward the anterior end, or toward both Figure 78. 

 ends. The head is small, and either naked, or \ 



with small papillae. The male has the posterior " | i. | 



end curved in a spiral, with membranous expan- /^^nljl I 

 sions, and with two unequal intromittent i ^%^,y // 

 spicules. In the female the posterior end of the x^^^^ 



body is nearly straight and conical, and the b — ^ 



ovary is either simple or double, with the genital 

 orifice situated at one side of the body. 



The 8. strongylina has a smooth, tapering body, with a 

 simple head and mouth. The male spicules are very long, 

 relatively to the entire length of the body. The male grows 

 to the length of half an inch or more. The female to more 

 than three-fourths of an inch. It lives in the stomach of the 

 hog, but ordinarily does not produce any serious disease. 



Figure 1'^.— -Spiroptera strongylina ; a, male, natural ^ize; h, .spicules and pos- 



terior end of the body, enlarged. From Guerin. 



