NO. 21;] 1. 



NEMATODE PARABITEf< OF RODENTS— HALL. 



11 



Fig. 7.— Tnicni- 

 nella spiralis . 

 posteeioe ex- 

 tremity of male, 

 showing clasp- 

 ing projections 

 and papillae, 

 e nlarged. 

 After Leuck- 



ART, 1866. 



3/a?e (fig. 5) 1.4 to 1.6 mm. long by 40 [i thick. The single testis 

 originates in the posterior portion of the body and extends ante- 

 riorly to about the posterior end of the esophagus ; here it turns back 

 and becomes the vesicula'seminalis, which terminates at the anal aper- 

 ture to form a cloaca. This terminal portion of the 

 vesicula and the cloaca can be protruded in copulation 

 (fig, 6). Two conical projections (fig. 7), 10 |U long, 

 are situated one on each side of the cloaca. These 

 are bent toward the ventral side and serve to hold the 

 female in copula. Between these lie four papillae, the 

 anterior pair hemispherical, the posterior pair conical. 

 Female (fig. 8) 3 to 4 mm. long by GO [jl thick. The 

 single ovary begins in the posterior end of the bod^^, 

 extends anteriorly for a short distance, and trans- 

 forms into the uterus, which is clothed with a small- 

 celled epithelium. The ovary and uterus appear to 

 be separated by a constriction. The uterus trans- 

 forms into the vagina near the posterior end of the 

 esophagus, and as such extends forw^ard to the vulva, 

 which is on the ventral side near the middle of the 

 esophagus and about one-fifth of the body length 

 from the anterior end. The eggs are subspherical 

 and are 40 by 30 [jl in diameter. There is a very deli- 

 cate vitelline membrane, but no true eggshell. The 

 embryos are developed in the uterus and escape from 

 the surrounding membrane while there. The em- 

 bryos are 100 to IGO \!. long by 9 ix 

 thick, the anterior end being the 

 thicker and the worm decreasing in 

 diameter toward the posterior end. 



Life hlstor}/. — The adult male and 

 female trichinae copulate in the in- 

 testine of the host animal. The 

 male then dies, while the female 

 bores into the mucosa, in the glands 

 of Lieberkiihn, and attains the 

 lymph spaces. Here the embryos 

 are deposited, beginning about a 

 week after the infection. The fe- 

 male lives five to six weeks longer 

 and bears during this time 1,^00 to 1,800 (Braun says 10,000) 

 embryos. In part actively and in part passively, the embryos make 

 their way by the lymphatic and blood channels throughout the en- 

 tire body and finally come to rest in the voluntary muscles, where 



Fig. 8.— Trichi- 

 nella spiralis. 

 Female. En- 

 larged. After 

 Leuckart, 18G6. 



