STRUCTURE OF THE CUTICLE. 599 



Having been convinced by previous experiments that the Echino- 

 coccus possessed a far slower development than other bladder-worms, 

 I determined to allow a longer time to a fourth animal, which had, 

 however, like the former ones, been used meanwhile in other experi- 

 ments (with Tcenia solium, T. marginata, and Trichina spiralis). The 

 examination was therefore not made until nineteen weeks after the 

 feeding. I hoped that after this lapse of time I should find the 

 Echinococci mature, and provided with heads ; but this time also my 

 hopes were doomed to disappointment. The experiment was certainly 

 successful, in so far as the liver (and it alone) contained between 

 thirty and forty bladders as large as nuts. On closer investigation 

 these proved to be Echinococci, but in spite of their size they were in 

 this case also still destitute of heads. Thus I had hitherto reared 

 mere acephalocysts, of exactly the same nature as those which Kuhn 

 has described with great accuracy in his above quoted monograph. 1 



In this case also most of these young encysted worms lay close 

 under the serous covering of the liver, through which they shone more 

 or less distinctly. Some had pushed out the covering before them 

 into a lump, so that only the lower half was embedded in the 

 substance of the liver. The adjacent parenchyma was of normal 

 appearance, and not distinguished by abundance of blood, nor in any 

 other way. 



All the more surprising was it that the capsular wall of the parasite 

 had in the meantime attained considerable thickness and firmness, 

 such as I had never observed in any other bladder-worms of the same 

 age. It was easily separable from the surrounding liver-substance, 

 and the outer layers also could easily be peeled off it. At the same 

 time its tension was so great that when cut it contracted powerfully, 

 and this rendered it extremely difficult to extract the parasite without 

 injuring its bladder. When this was successfully accomplished, 2 the 

 worm appeared in the form of a transparent bladder of fluid, either 

 round or nearly so ; that is, of course, when the bladder was suspended 

 in water. If placed on a firm surface it flattened out into a cushion- 

 like shape, proving that the surrounding membrane possessed only a 

 limited power of resistance. The average diameter amounted to some- 

 thing like 10 to 12 mm., but varied from 3 to 18 mm. 



Here and there the otherwise transparent character of the bladder- 

 worm was dimmed by a thin white margin, which was situated on 

 the cuticle, and which, by the aid of the microscope, was recognisable 

 as a portion of the layer of cells enveloping the connective-tissue cyst. 



1 M6m. soc. hist. nat. Strassb., t. i., 1830. 



2 I recommend for this purpose dissecting under water a method which has enabled 

 me to extract Echinococci larger than the fist, uninjured from their capsules. 



