TRICHINELLID^E 



301 



m 



in the cecum of dogs suffering from ankylostomiasis, but have an in- 

 significant secondary part to Ankylostoma canina as a cause of this 

 affection. 



Trichinosis 



Trichinella spiralis (Trichina spiralis). Fig. 162. Trichinellidte 

 (p. 299). — A ver}^ small worm with bodj^ somewhat thicker posteriorly, 

 hut without abruptly demarcated fila- ^ g 



mentous anterior as in the Trichurinse. 

 The mouth is round and unarmed. The 

 esophageal portion extends to about one- 

 half of the length of the body, the esoph- 

 agus embedded in a chain of single cells. 

 The portion of the body posterior to the 

 esophageal contains the intestine which 

 ends in a terminal anus. The single 

 testis of the male originates posteriorly 

 and extends forward to the esophagus 

 where it turns back and becomes the 

 seminal vesicle which terminates at the 

 anal aperture. The cloaca thus formed 

 has on each side of its opening two pro- 

 jections which serve to clasp the female, 

 the cloaca being extruded in copulation. 

 There is no spicule. The single ovary 

 of the female begins posteriorly and, ex- 

 tending forward for a short distance, be- 

 comes the uterus. The vulva is about 

 one-fifth of the length of the body from 

 the anterior end. 



The female is 3^ mm. (1/8-5/32 of an 

 inch) in length; male, 1.4-1.6 mm. (1/16 

 of an inch). 



The embryos are developed within the 

 uterus and are hatched there by breaking 

 through the delicate membrane sur- 

 rounding the egg. From the uterus and 

 vagina they pass from the body of the, 

 mother worm through the vulva. The 

 hatched embryos are 100-160 microns 

 long by 9 microns thick, the anterior end 

 somewhat thicker than the posterior. 



Parasitic as adults in the small intestine and as larvae in the muscula 

 ture of hogs, rats, mice, and other mammals, including man. 



Fig. 162.— Trichinella 

 male at left, female at 

 much enlarged. 



spiralis- 

 right, — 



