ECHINOCOCCUS ALTRICIPARIENS. 209 



The characteristics of this species of Echinococcus, as dis- 

 tinguished from the preceding, are as follows : 



1. The enveloping cyst, and the mode of annexation of the 

 inner wall of this cyst to the primary vesicle of the Echinococcus 

 derived from the six-hooked embryo, are similar in this and 

 the foregoing species, but the cyst formed by E.altricip. is much 

 larger than that of E. scolicipariens, and for this reason projects 

 far above the level of the organ in which the colony sits. 



2. From its much greater size results a proportionately in- 

 creased interference with the functions of the organ attacked, 

 and eventually of the whole organism. 



3. With regard to the animal itself this distinction occurs, 

 that we not only find single scolices or a single vesicle in such a 

 colony, but that we have here to do with the constant production 

 of fresh vesicles with young (daughter- and granddaughter- 

 vesicles), sometimes with, and sometimes without, the production 

 of separate scolices adhering directly to the walls of the vesicle. 

 That the hydatids occurring in Iceland exclusively exhibit this 

 structure appears from the case furnished by Thorstensen to 

 Schleissner, as well as from the following remarks which are 

 quoted from Schleissner. " The hydatid-sacs are formed not only 

 in the human liver, but in very many parts of the abdomen, 

 and are often of enormous size. Hundreds of hydatids are 

 frequently evacuated through the external opening of the sac, 

 or with the stool, and in vomiting. They do not, however, occur 

 only in the interior of the body, but also very frequently in the 

 skin, where they appear like large saccular swellings. The 

 course of the disorder is very chronic." In this description I 

 have purposely avoided the words " production of similar vesicles 

 in themselves," as the vesicles produced do not, like the original 

 mother-vesicle, bear six embryonal hooklets, which these secon- 

 dary and tertiary vesicles certainly never possess at any period 

 of their existence, as they never have occasion for them. More- 

 over, it is unnecessary for me to state particularly that the six 

 hooklets may be sought for in vain even on the mother-vesicle, 

 as although they are certainly present, they must, from their 

 extreme minuteness, escape the eye on such a large vesicle, or 

 in its enveloping cyst. The smallest of the granddaughter- 

 vesicles are but just visible; they are about half the size of a 

 pin's head, and enclose four, five, or more scolices, which adhere 

 peripherically, by a small stalk, to the inner wall of the common 



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