1 98 ON THE ANATOMY OF ECHINOCOCCUS VETERINORUM 



distinguished into two portions. The outer is thick, yellowish and 

 constituted by a great number of delicate, structureless laminae com- 

 posed of a substance closel)- resembling Chitin. It is to this laminated 

 membrane that the elasticity of the C)'sts is due — and it must be 

 regarded as precisely analogous to those structureless cysts which 

 surround the pupa forms of Distoinata imbedded in the body of 

 snails, or to those similarly structureless cysts which enclose the 

 encysted Tetrarliynchi, and which Van Beneden saw in course of 

 formation by a process of exudation, around the Scolex form of those 

 worms. The innermost layer of this, which, for distinction's sake, I 

 will call the Edocyst, is whiter and softer than the others, and appears 

 to be in course of formation. 



The inner portion of the wall of the E chinococais-cy st is closely 

 adherent to the last described laj-er of the ectocyst, but may, with 

 great care, be separated from it, when it is at once evident that 

 there is no organic connexion between the two ; this layer may be 

 very conveniently termed the endocyst — it is the only active living 

 part of the whole wall of the cyst, and represents the proper bod}'- 

 wall of the animal. It is very pale and delicate, and not more than 

 „i__th of an inch thick (PL XXVIII. [Plate 21] fig. 5). It is composed 

 of very delicate cells o-jig- xr ~ t injTrth of an inch in diameter, without ob- 

 vious nuclei, but often containing clear, strongly refracting corpuscles, 

 generally a single one only, in a cell. These corpuscles appear to 

 be solid, but by the action of dilute acetic acid, the interior generally 

 clears up very rapidl)-, and a hollow vesicle is left of the same size as 

 the original corpuscle. No gas is developed during this process, and 

 sometimes the corpuscles are not acted upon at all by the acid, appear- 

 ing then to be of a fatty nature. A strong solution of caustic ammonia 

 produces a concentrically laminated or fissured appearance in them. 

 Under pressure, and with commencing putrefaction, a number of them 

 sometimes flow together into an irregular or rounded mass. 



The inner surface of the endocyst is sometimes irregularly papil- 

 lated like a glandular epithelium in consequence of the prominence 

 of separate cells (PI. XXVIII. [Plate 21] fig. 5), or its surface presents 

 an even contour, from the presence of a structureless membrane, 

 which varies in thickness, and seems to represent the inner portion 

 of the blastema, elsewhere slightly granular, in which the cells are 

 imbedded (PI. XXVIII. [Plate 21] fig. 2). 



Solitary hooks are scattered over the inner surface of the endocyst. 

 I thought at first that they had fallen from the EcJiinococci ; but it 

 is with some difficulty that, even by the aid of pressure, the hooks 

 can be so detached from them ; and furthermore the hooks in question 



