NE3IATODA. 



358 



Sc. tetracanthwn Mehlis, also in the intestine of the horse. The embryos, after 

 migrating into the intestine, become encysted in the walls of the rectum and 

 caecum, assume within the cyst their definite form, break out from the cyst, 

 and escape again into the intestine. Gacnllanus elegans Zed., in the Perch. 



Fam. Trichotrachelidae, with long neck-like thin anterior portion of the 

 body. Mouth small, without papillae. (Esophagus very long, traversing a 

 peculiar cord of cells. 



Tricliocephalus Goeze. Anterior part (fig. 285) of the body elongated and 

 whip shaped : posterior part cylindrical and sharply distinct, enclosing the 

 generative organs, in the male it is coiled up. Lateral lines absent. Main 

 median lines present. The penis is slender and furnished with a sheath, which 

 is turned inside out when the former is protruded. The hard-shelled, lemon-shaped 

 eggs undergo the first part of their development in water. Tr. dispar Bud. In 

 the human colon : these worms do not live free in the intestine, but bury their 

 filiform anterior extremity in 

 the mucous membrane (fig. 

 285). The eggs pass out of the 

 host with the fasces, as yet 

 without a sign of beginning 

 development, which only takes 

 place after a prolonged sojourn 

 in the water or in a damp 

 place. According to the ex- 

 periments of Leuckart per- 

 formed with Tr. affinis of the 

 sheep and Tr. crenatus of the 

 pig, embryos with the egg 

 membranes, if introduced into 

 the intestine, develop into the 

 adult Tricoceplialus ; and we 

 may therefore conclude that 

 the human Tr. dispar is intro- 

 duced directly, and without an 

 intermediate host either in the 

 drinking water or in uncleaned 

 food. The young Tr. dispar 

 is at first hair-like, and re- 

 sembles a Trichina, and only 

 gradually acquires the considerable thickness of the hind end of the body. 



Tricliosomum Kud. Body thin, hair-like, but the posterior end of the body 

 in the female is swollen. Lateral lines and the principal median lines are 

 present. The male caudal extremity has a cutaneous fold and a simple penis 

 (spiculum) and sheath. Tr. muris Creplin., in the large intestine of the 

 house-mouse. Tr. crassicauda Bellingh., in the bladder of the rat. According 

 to Leuckart, the dwarfed male lives in the uterus of the female. There are 

 usually two or three, more rarely four or five males in a single female. There 

 is also a second species of Tricliosomum found in the bladder of the rat. 

 Tr. Sclimidtii v. Linst, the larger male of which was formerly taken for that of 

 Tr. crassicauda. 



Trichina Owen.* Body thin, hair-like. Principal median lines and lateral 

 * Compare the writings of R. Leuckart, Zenker. R. Virchow, Pagenstecher, etc. 



23 



FlG. 285.Trichoceplialiis dispar (after R. Leuckart). 

 a, Egg ; 6, female ; c, male with the anterior part of 

 the body buried in the mucous membrane; Sp, 

 spiculum. 



