234 ANIMAL PARASITES. 



of cystic worms, and it is certainly obvious that in such districts 

 double care is necessary. But moisture alone cannot be the 

 cause of the cystic worms — for this we require the eggs of 

 particular Teenies with their six-hooked embryos. As regards 

 Echinococcus scolicipariens , the inference founded on analogy is 

 easy. We know that with such an extraordinary development of 

 the breeding of cattle and sheep, for which dogs are required, it 

 cannot be difficult for the dogs to infect themselves with those 

 Teenies belonging to the cystic worms of the sheep, which are 

 slaughtered in great numbers in Iceland — such as Tcenia Ccenurus, 

 T. Echinococcus veterinorum of authors, and T. e Cysticerco tenui- 

 colli. Man, also, may easily acquire an Echinococcus scolicipariens, 

 from the eggs which have escaped externally, as we have 

 already seen, and as we shall soon see more distinctly ; and the 

 more numerous the dogs are, the more will such Tcenia be 

 present, and their eggs escape into the outer world. The more 

 frequently also will the opportunity be given for these eggs 

 to find their way into the human subject, if no hinderance of 

 any peculiar kind exists. But it requires a further explanation, 

 and a deeper investigation of the local conditions, to discover 

 how Echinococcus altricipariens is produced in the human subject, 

 and how it can propagate itself. 



Where, we may ask, in the first place, does the mature Taenia 

 belonging to this species take up its abode ? Its dwelling-places, 

 in my opinion, can only be two, namely, the intestine of man 

 himself and that of the dog ; in the latter of which situations, 

 indeed, most of the cystic worms which occur in the larger 

 domestic mammalia, can develope themselves into Teenies. As a 

 matter of course, a man suffering from Echinococci may infect 

 himself with T. Echinococcus, by the bursting of his Echinococcus- 

 colony in the direction of the intestine, where the scolices con- 

 tained in the daughter-vesicles are poured out, and become 

 Tcenia. But, after what we have already said upon Tcenia solium, 

 it is equally evident that just as a person who harbours a 

 T. solium may infect himself with Cysticercus celluloses, the bearer 

 of Tcenia Echinococcus will also be in a condition to infect him- 

 self with Echinococci. In such cases we should easily explain 

 the increase of the Echinococcus-tumours with age in certain 

 individuals, and their constant new formation. Besides, the views 

 here laid down agree with our further observations in Iceland, 

 where, according to the few known exact histories of patients, 



