112 



corpuscle. No gas is developed during this process, and sometimes 

 the corpuscles are not acted upon at all by the acid, appearing then 

 to he of a fatty nature. A strong solution of caustic ammonia pro- 

 duces 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. 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 bla- 

 stema, elsewhere slightly granular, in which the cells are imbedded 

 (PL XXVIII. fig. 2). 



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

 I thought at first that they had fallen from the Echinococci ; 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 

 had generally the appearance of those forms found in the younger Echi- 

 nococci, from which there is still greater difficulty in detaching them. 

 I conclude then that these hooks are developed where they are found, 

 and that they represent a sort of attempt to develope an EchinocQccus 

 which has gone no further. Within the substance of the endocyst 

 one may see here and there traces of clear delicate vessels, such as 

 those which will be described in the secondary cysts ; but probably 

 in consequence of the granular nature of the membrane, they are 

 rarely visible. 



In describing the development of the Echinococci, it vrill be neces- 

 sary to return to this endocyst — at present I pass to the contents of 

 the cyst. This is a clear, colourless, serous liquid, in which two 

 kinds of bodies are found floating, a. Echinococci, and b. secondary 

 cysts. 



a. Echinococci (PI. XXVIII. fig. 1). To avoid circumlocution, I 

 restrict this term in the present place to what are commonly called 

 the EchinococcusAxQ&diS. 



The Echinococci are minute, oval bodies, varying, according to the 

 state of contraction in which they are found, from 2^— g^th of an 

 inch in their long diameter. 



When fully extended, the Echinococci are divided by a constriction 

 into two portions ; an anterior somewhat conical part, and a posterior 

 oval portion, notched at the extremity; attached to the posterior sec- 

 tion, and, as it were, sunk in the notch, there is a small appendage 

 of variable form, which visually appears to be clear and somewhat oval 

 or pyriform, with an irregular ragged extremity. 



The body of the Echinococcus consists of a very clear transparent 

 substance, slightly granular or dotted internally, and limited exter- 

 nally by a well-marked structureless layer. Forming a circle round 

 the conical anterior extremity there are from twenty to thirty strong 

 hooks, which sometimes appeared to be in a single, sometimes in a 

 double row. In the latter case the hooks of the upper row alternated 

 with those of the lower. A delicate longitudinal striation, as if pro- 



