THE RECEPTACLE AND ITS ANATOMICAL RELATIONS. 



347 



elevation and growth of the head, or, in other words, that the receptacle 

 is formed by further differentiation of the muscular layer of the 

 "bladder, just as the head proper is formed from the suhcuticular 

 sheath. Nor can the receptacle and head be distinguished so sharply 

 from one another as is at first apparently the case. As the muscular 

 sheath and the cellular layer are bound together in the wall of the 

 bladder, so we can always demonstrate a connection between the 

 receptacle and its contents (Fig. 197), a connection which extends 

 over the whole surface, or is in some species confined to certain 

 points. 



Thus the receptacle is not in every case an equally independent 

 structure. It has least independence in the bladder- worms with paren- 

 chymatous bodies, such as we have seen in Cysticercus (Piestocystis) vari- 

 dbilis and its allies, for there it is 

 not only connected with the mass 

 of the head, but is, like the ordi- 

 nary body muscles, bound up with 

 the tissue of the bladder. One 

 can observe how the muscular 

 sheath which runs between the 

 cortex and the inner parenchyma 

 (Fig. 19 7) bends backwards at the 

 anterior end, and surrounds the 

 head as a sac, and how the in- 

 dividual fibres Often Separate FIG 189. -Cephalic end of a young bladder- 



worm from the rabbit, showing the still im- 

 themselves from the receptacle, perfectly developed hooks. ( x 45.) 



and mingle with the parenchyma. 



The state of matters is very similar in Cysticercus pisiformis where 

 the bladder- worm body preserves anteriorly its original parenchyma- 

 tous character, so that the receptacle is united on all sides to a loose 

 connective substance. The only difference which can be observed is 

 that the fibres of the receptacle are more closely appressed and more 

 firmly interwoven. 



Where the inner parenchyma is wholly obliterated by the accumu- 

 lating water, as in the majority of true bladder- worms, the receptacle 

 of course acquires a distinct external boundary. The connection with 

 the body of the bladder becomes in such cases restricted to the basal 

 portion of the head, where one can observe the fibres passing directly 

 into the muscular sheath. 



As a rule, however, it is only the exterior surface of the receptacle 

 which attains this independence ; for the inner surface remains usually 

 in general, though, as we shall afterwards see (Fig. 197), in loose 

 connection with the head. The bladder- worm of Tcenia solium, the 



