ON THE ANATOMY OF ECHINOCOCCUS VETERINORUM I99 



had generally the appearance of those forms found in the younger 

 Echinococci, 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 Edii- 

 nococais 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 Echiiiococci, it will 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. Ec/iinococci, and b. secondary cysts. 



a. Ecliinococci (PL XXVIII. [Plate 21] fig. i.) To avoid cir- 

 cumlocution, I restrict this term in the present place to what are 

 commonly called the EcIiinococcus-\i<fA.As. 



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

 state of contraction in which they are found, from ^-^0 — y'j-th of an 

 inch in their long diameter. 



When fully extended, the Ecliinococci are divided by a constriction 

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

 oval portion, notched at the e.xtremity ; attached to the posterior sec- 

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

 variable form, which usually appears to be clear and somewhat oi^al or 

 pyriform, with an irregular ragged extremity. 



The body of the Ecliinococcus 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- 

 duced by muscular fibres, extends from the circlet of hooks through 

 the anterior portion, becoming spread out and lost in the posterior. 



The hooks (fig. 3) were about -Joth of an inch in diameter. Their 

 outer half was formed by a strong, curved, conical claw, the inner half 

 by a somewhat crooked process with a blunt end. From the posterior 

 surface of the junction of these two portions a strong rounded spur 

 passed backwards and gave the hook additional firmness in its place. 

 The hook contained a cavity, a process of which passed into each of 

 its portions. Altogether it was not unlike the thickened liber-cell of 

 a plant. 



