HISTORY OF THE ECHINOCOCCUS. 583 



There were, in other words, two distinct sources, from either of which 

 man might be infected. 



Being unable to identify the hypothetical Tcenia of Echinococcus 

 altricipariens with T. echinococcus, Kiichenmeister maintained on 

 purely theoretical grounds that the former lived preferably in the 

 human intestine, 1 and that thus the Echinococcus altricipariens, which 

 is by far the commonest form of the human Echinococcus, sprang from 

 a human tape-worm, and was perhaps only rarely brought to us 

 through the dog. My opinion has, however, in course of time, found 

 not only acceptance, but experimental demonstration. This has been 

 supplied by the above-cited observations of Krabbe, to which I may 

 again refer as important completions of my own researches. 



Even Kiichenmeister has not been able any longer to resist the 

 force of established facts. In the new edition of his work on 

 parasites 2 he concedes with apparent unwillingness that the different 

 forms of Echinococcus are but varieties of the same species (T. 

 echinococcus). 



Since the Echinococcus-bldiddQTS have almost no power of motion 

 in consequence of the considerable thickness of the cuticle, and the 

 extremely slight development of their muscle-fibres, and since their 

 heads are only recognisable on microscopic examination, we can 

 understand that their animal nature was established somewhat later 

 than was the case with the other bladder - worms, though their 

 existence and medicinal importance were much sooner recognised. 

 Even in Hippocrates we find passages which refer to this Echinococcus, 

 and in the writings of the physicians of the sixteenth and seventeenth 

 centuries we find descriptions of the so-called "Hydatids," which 

 give a correct and full statement of the external characters of the 

 organism. 3 Pallas was, however, the first (1767) to recognise in these 

 vibrating hydatids independent organisms allied to the bladder- 



1 We shall afterwards see that Kiichenmeister has not even yet shaken himself free 

 from this utterly groundless opinion. 



2 On page 162 he says, "I do not by any means contend that all the varieties of 

 Echinococcus represent distinct species of Tcenia." For one who formerly maintained 

 unequivocally the specific distinctions between these "varieties," this is a withdrawal 

 without any express acknowledgment of error. The change in the form of the hooks, so 

 characteristic of T. echinococcus, receives no further mention, except what we find on page 

 136, where Kuchenmeister, in discussing the question whether the differences in the 

 structure of the hooks between Cysticercus acanthotrias and C. ceUulosce are sufficient to 

 establish a specific distinction, says, " If the structure of the hooks in the different forms 

 of T. echinococcus be considered as varying with the individual hosts, and not merely with 

 their systematic position (sic/), the same view might be adopted here." 



3 Other such cases are collected by Pallas (Neue nord. Beitrdge, Th. i, p. 84), by 

 Leuckart (" Blasenbandwurmer," p. 4), Davaine (loc. cit., p. 350), and by Kuchenmeister 

 ("Parasiten," second edition, p. 56, note), and still more thoroughly in the Deutsch. 

 Archivf. Geschichte d. Med., Bd. ii. u. iii. 



