162 MEDICAL ZOOLOGY. 



T. spiralis. Body rounded and filiform ; usually slightly bent upon itself, 

 rather thicker behind than in front, especially in the males; head narrow, 

 finely pointed, unarmed, with a simple, central, minute oral aperture. Male 

 possesses a bi-lobed caudal appendage, the anal aperture situated between its 

 lobes ; penis, consisting of a single spicule, cleft above to assume a Y-shaped 

 outline. Female stouter than male, bluntly rounded posteriorly ; genital pore 

 at anterior fifth of body. 



Measurements. Male, T y long ; female, ". 



Habitat. Intestine of man and hog. 



Development. The mature female inhabiting the intestine, after producing 

 active young, dies and is removed with the ejecta. But the embryos remain 

 within the host, very soon to penetrate the walls of its intestine. After 

 assuming the desired position among the tissues they become encapsuled 

 and remain quiescent. When a portion of flesh thus inhabited is consumed 

 by another animal the larvae again become active within its alimentary 

 canal, and soon take on the sexual form. Coition now occurring, the female 

 brings forth broods of larvae as before. The conditions attendant upon the 

 passage of large numbers of larvae from the intestine to the surrounding 

 tissues constitutes the disease Trichiniasis. 



The most conspicuous instances of the disorder are seen when the infected 

 flesh of the hog is eaten, either raw or imperfectly cooked, by man. 



Strongylus. Body subcylindrical, rarely prismatic ; attenuated at either 

 end. Head naked, continuous with the body ; rarely alate. Mouth term- 

 inal, orbicular limb not horny, naked or papillose. Caudal extremity of 

 male with terminal entire bursa, truncate ; with one or more radiated setae. 

 Penis filiform, contained within a bi-partite sheath. Genital pore of female 

 placed anteriorly, rarely posteriorly. (Diesing.) 



S. bronchialis, Cobbold. Caudal appendage with a bi-lobed membranous 

 semi-bell-shaped bursa (supposed to be an accessory organ of copulation) 

 which surrounds the cloacal outlet. Penis a double spiculum lying in cloaca. 

 Female, tail sharply pointed, anus little in front or above the narrow part ; 

 body filiform, pale yellow color, ^ of an inch broad; viviparous. 



Measurements. Male, 6'" long, -fa" wide; female, 1" long, 5 y wide. 



Dis. by Treutler, Germany, 1791, in the bronchial glands of an emaciated 

 subject. Confined to the air-passages. 



Tricocephalus. Body subcylindrical, rather thick. Male mostly spiral ; 

 female straightish. Neck very long, gradually thickening posteriorly. Head 

 scarcely distinct. Caudal bursa rarely unarmed, with a filiform penis with- 

 drawn within a retractile sheath. End of tail of female straight and some- 

 what obtuse ; genital aperture at base of neck. (Diesiug.) 



T.dispar, Rudolphi. Male, long; neck, two-thirds length of body; skin 

 with wart-like appendages on one side only; tail curved, emitting at extrem- 



