Z9 8 



/OOLOGY FOR MKDTCAL STUDENTS 



CHAP. 



. .isily through the capillary network but when they find 



.raversing the capillaries of a muscle particularly if it be one 



nt tlu- nit in- act i vi- muscles such as the diaphragm they bore their way 



the capillary and pass in amongst the muscle fibres. After 



spending sonic time, it may be several days, migrating through the 



. tin- young worm curls itself up into a spiral and settles down in 



nditicm between the muscle fibres (Fig. 89), the connective 



<>uml it reacting to its presence by enclosing it in a lemon-shaped 



iin.nl -4 mm. in length. 



Within its cyst tin- young Trichina may retain its vitality for many 



T. 



mf. 



FIG. 89. 

 Larval Trichinae encysted in muscle. X 26. m.f, Muscle fibres ; T, Trichinae. 



.in this is unusual and as a rule after a few months or years the 



calcification. 



No lurther development takes place unless the muscle containing the 



Trichina is swallowed by a suitable animal. When this happens the 



worm is set tree by the digestion of the cyst : it rapidly within 



from one to two days attains to sexual maturity and the life-cycle is 



I afresh. 



particularly liable to become infected, probably through 

 the flesh of an infected rat, and then the infection is liable to be 

 "! tn man by his eating insufficiently cooked pork or ham con- 

 taming the encysted worms. As the infection is liable to be a heavy 

 'ill in- in the presence of many millions of young worms within 

 re .symptoms of disease (trichinosis) are produced more 

 h.l-ra-likr symptoms during the intestinal stage, and high tem- 

 "Uipanied by severe muscular pains (luring the period of 



