220 ENTOZOA. 



CHAPTER V. 



T^NIA SOLIUM. 



Development of the common tapeworm — The life phases of Tisnia solium regarded as 

 parts of the " zoological individual " — Injurious effects upon man — Particular 

 instances — Frequency of Oysticeroi in the human brain — Mr. Hulke's case — Pre- 

 cautions suggested — Statistics — Treatment. 



Having devoted an entire cTiapter to the consideration of the 

 general characteristics and structure of the common tapeworm, 

 both in its adult and larval conditions, I proceed, in as brief a man- 

 ner as possible, to give an epitomised view of the developmental 

 changes and wanderings which are undergone by this species in its 

 passage from the free proglottis condition into the ordinary, sexu- 

 ally mature Tcenia solium. A part of these life-changes have 

 been indicated already, but their intermutual relations have now 

 to be described and explained under a separate head. 



Development. — After the proglottis (which, it must be borne in 

 mind, is furnished with male and female reproductive organs) has 

 undergone impregnation by contact with another proglottis, there 

 results from this the formation of eggs within it, which eggs, 

 whilst still within the body of the parent, develop into embryos, 

 the latter still retaining the egg coverings. At this time the pro- 

 glottis is about to undergo a passive migration, and having de- 

 tached itself from the strobila, it is soon expelled from the bowel of 

 the host, thus finding its way into some cesspool, or, it may be, into 

 the open fields. The proglottides move about for a time, but the 

 growth of the multitude of embryos within their interior causes the 



