DIGESTIVE SYSTEM 121 



end very thin and liair-like, the posterior extremity being thicker 

 and thread-like. They are usually coiled, and are from one to one 

 and one-quarter inches in length. Their life cycle is similar to that 

 of the Esophagostoma. Infestation is accomplished through the food 

 or drink. 



Lesions. — The Trichocephali are blood suckers, but they appear 

 to do very little damage unless they occur in large numbers. When 

 they produce anemia there is also more or less intestinal catarrh. 

 The parasites are found firmly attached to the mucous membrane 

 of the large intestine. 



Symptoms. — The principal symptoms are diarrhea, emaciation, and 

 weakness. 



Treatment. — Practically the same as described for the Ascaris 

 suum. 



Trichivella Spiralis 



Trichinella spiralis passes only the adult stage of its life cycle in 

 the intestine. The larvae are important muscle parasites. Further 

 discussion vs^ill be found under "Muscular Parasites." 



Gigantorhynchus Hirudinaceus 



This, the thorn-headed intestinal worm of swine, is quite preva- 

 lent in practically all sections of this country. It is a thick, cylin- 

 drical, white worm with an attenuated tail portion, transverse mark- 

 ings, and a head provided with a globular proboscis having several 

 rows of hooks. The ova pass to the ground with the feces and are 

 ingested by the larva of the May beetle, in which it passes a portibn 

 of its life cycle, the embryo and larval stages. Hogs consume the May- 

 beetle larva and the inclosed gigantorhynchus larva is liberated and 

 passes into and attaches to the intestine of the hog. It is thought 

 that the ova may develop elsewhere as well as in the May-beetle larva. 



Lesions. — Upon opening the abdomen of a swine infested with 

 the Gigantorhynchus, shiny nodules of a grayish color are readily 

 visible on the serous coat of the intestine. The thorn of the worm 

 is found to have penetrated the mucosa, and thus permits of infec- 

 tion which results in the production of an inflammatory zone. The 

 parasites may become detached, the lesions produced having healed bj 

 the formation of cicatricial tissue, which is usually easily recognized 

 Not infrequently the head of the parasite bores through the entire 

 intesinal wall and occasions general peritonitis. 



