350 



THE ANIMAL PARASITES OF MAN 



A large hydatid may contain many thousands of brood capsules. 

 Each brood capsule is about as big as a pin's head, and may contain 

 ten to thirty or more scolices. The delicate wall of the brood capsules 

 may rupture, so that the scolices are now free in the mother cyst. These 

 free scolices and also free brood capsules constitute what is known as 

 " hydatid sand," which settles at the bottom of a glass when hydatid 

 fluid is poured into it. This form occurs chiefly in domesticated 

 animals and is termed E. veterinornui, Rud., or E. cysticus fertilis. 



In man, and only rarely in cattle, the mother cyst first forms 

 " daughter cysts" (E. hominis, Rud. [fig. 255]), which, though smaller 

 than the " mother cyst," re- 

 semble it in the structure of 

 their walls ; thus they are 

 covered externally by a lami- 

 nated cuticle and internally 

 by the parenchymatous layer. 

 They originate : 



FIG. 253. Section through 

 an invaginated echinococcus 

 scolex. Cf. fig. 252A, 7. x 300. 

 (After Deve.) 



FIG. 254. A piece of the wall of an Echinococcus 

 veterinorum stretched out and seen from the internal 

 surface. A few brood capsules (the outline of which 

 is only faintly shown), with scolices directed towards 

 their interior and exterior. 50/1. 



(1) Between the laminae of the cuticle of the mother cyst from 

 small, detached portions of the parenchymatous layer ; during their 

 growth they bulge inwardly or outwardly and may separate them- 

 selves entirely from their parent cyst. In the latter case they lie 

 between the mother cyst and the capsule of connective tissue 

 formed by the host (E. granulosiis or E. hydatidosus exogenus) ; 

 when growing inwardly they reach the interior of the mother cyst 

 (E. hydatidosus endogenus). Their number is very variable and does 

 not depend on the size of the mother cyst. They are as big as, or 

 bigger than, gooseberries. 



(2) According to some authors, endogenous daughter cysts arise also 



