THE DIGESTIVE SYSTEM 51 



blacksnake whip, the head end very thin and hair-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. 



Trichinella Spiralis 



Trichinella spiralis passes only the adult stage of its 

 life cycle in the intestine. The larvae are important 

 muscle parasites. Further discussion will be found 

 under "Muscular Parasites," on page 142. 



Gigantorhynchus Hirudinaceus 



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

 quite prevalent in practically all sections of this country. 

 It is a thick, cylindrical, white worm with an attenuated 

 tail portion, transverse markings, 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 

 portion 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 



