140 



ANIMAL PARASITES. 



their way, through the mucous membrane and wall of the gut, into vari- 

 ous parts of the body. 



The exact course which they take in getting out of the gut is not fully 

 established; probably they traverse the tissues in different ways. At 



any rate, they find their way 



trasss**. ' 

 m 



jT 



FIG. 07. TRICHINA SPIRALIS. 



to the voluntary striated 

 muscle tissue, which they 

 penetrate, and enter the 

 muscle fibres. Here they 

 cause a disintegration of the 

 contractile substance, and 

 coil themselves inside of the 

 sarcolemma. In this situa- 

 tion they become encapsu- 

 lated by material in part 

 furnished by themselves, in 

 part by means of the inflam- 

 matory reaction which their 



The parasites are encysted in muscle. In one capsule the presence induces ill the COU- 

 parasite has died, and the grauu.ar materia. replacing it is ca.- nectiye tigsue of the musc l e . 



The worms are surrounded 



inside the capsule by granular material (Fig. 67). The capsule after 

 a time becomes partially calcified, and in this condition may be readily 

 seen by the naked eye as a tiny while speck. In this encysted state they 

 may remain inactive but living for an indefinite, often for a very long- 

 time. Most frequently the cysts contain but one embryo, but they may 

 contain from two to four. The embryo may die and its remains become 

 calcified. 



The same course of events follows when the muscle trichinae are eaten 

 by the pig or a variety of other animals. 



The embryos in the muscle are killed by a temperature of 55 C. and 

 by some of the methods of curing pork. 



The embryos may mature and a new generation be born within from 

 five to eight days after the ingestion of the diseased meat. 



At the result of the presence of these parasites in the body, if the 

 invasion be severe, nutrition may be impaired and catarrhal enteritis, 

 broncho-pneumonia, hyperplasia of the mesenteric lymph nodes, and fatty 

 degeneration of the liver may occur. Leucocytosis with a great increase 

 in the number of eosinophile cells is common. The encapsulated em- 

 bryos may be found in enormous numbers in various voluntary muscles 

 of the body, but they are most apt to be found, when not very abundant, 

 in the muscles of the neck and larynx, in the intercostals and the dia- 

 phragm. They tend to collect toward the tendinous extremities of the 

 muscles. Trichinae also occur in the rat, cat, mouse, and other animals. 



Fllaria medinenis (Guinea worm). This is a thread-like worm; the 

 female, which is alone known, being sometimes as much as 80 cm. long 

 and from 0.5 to 1.7 mm. thick. It is common in the East, and inhabits 

 the subcutaneous connective tissue, in which it often gives rise to ab- 



