109 



distributed in the blood throughout the body. They 

 penetrate the capillary walls and invade the muscles, par- 

 ticularly those of the tongue, diaphragm, intercostal region, 

 and abdomen. In the muscle tissue the larvae coil them- 

 selves up and encyst. The cyst, which may contain one or 

 several larvae, is formed by the inflamed connective tissue ; 

 it is oval and membranous, but after a time it becomes 

 limy. There may be many millions of these cysts, and 

 within them the larvae remain quiescent until their host is 

 eaten by a new host. If a rat thus infested is devoured 

 by a pig, the cysts are dissolved in the pig's stomach, and 

 the larvae, thus set free, become sexually mature in two 

 or three days' time. Pigs are also infected when fed with 

 the offal from " trichinosed " pigs. 



When the encysted larvae are accidently swallowed by 

 Man, by eating trichinosed pork undercooked, development 

 follows as already described. 



The presence of the adult Trichinae in the small intestine 

 causes gastro-intestinal disorder. The invasion of the 

 muscles by the larvae results in degeneration of the fibres, 

 and inflammation, fever, and oedema ensue ; later there is 

 marked cachexia. 



Fm. 24. - Trichinosed " Pork. (Magnified.) 

 Showing encysted larvae of Trichina spiralis. 



