642 OCCURRENCE AND MEDICAL IMPORTANCE. 



A fact that is still more remarkable than this preponderance of 

 the female JZchinococcus-hosts, is that more than half of the cases of 

 Echinococcus multilocularis which have hitherto been observed in man 

 (nineteen cases among thirty-five, according to Niesser) belong to 

 Switzerland ; and in Germany this form has been found almost ex- 

 clusively in the south, so that a case observed in Dorpat is quite an 

 exception. Yet these countries are precisely the ones in which 

 Echinococcus is otherwise rare. We can hardly agree with Klebs in 

 supposing that the reason of this peculiar phenomenon is to be found 

 in the prevalence of cattle-breeding, since the most that could be 

 inferred from this would be a frequent occurrence of the Echinococcus. 

 Perhaps, after we have learned the causes that give the Echinococcus 

 multilocularis its peculiar form, 1 we shall find a better explanation. 

 In the meantime we have so little light on the subject that we do not 

 even know whether the determinant factors are to be found in the 

 worm itself, or, as is certainly more probable, in the condition of the 

 environment (abode, nature of the enveloping cyst, &c.). 



In regard to the age of patients suffering from Echinococcus, it is 

 quite certain from the reports of Neisser that, like Cysticercus celluloses, 

 the parasite occurs most frequently in persons between twenty and 

 thirty. No fewer than 55 per cent, are found within this period, 

 while the rest are distributed over various other ages, up to fifty and 

 sixty, but always occur in greatest numbers near the former age. It 

 is doubtful whether the infection also takes place within this time, 

 especially as we know that the Echinococcus grows but slowly, and 

 usually only causes great disturbances of health after an existence of 

 some years. For the same reason it is extremely rare for it to occur 

 in early childhood. Finsen operated on a boy of six, who had 

 harboured the Echinococcus since his first year; and Thorstensen 

 reports the case of a child of four, in whom the extirpated bladder- 

 worm (E. hydatidosus) had already attained the size of a child's 

 head. 2 



So far as I know, these are the youngest, reliable cases of Echino- 

 coccus patients. It is, indeed, stated by Hammer that, in the case of 

 a newly born child, whose much distended abdomen proved a 



multiple Echinococci have occurred almost exclusively in the female sex. Kiichenmeister 

 connects this fact with the looseness of the peritoneal covering of the female sexual organs, 

 which he thinks possibly favours the development of the parasite. 



1 Morin finds the explanation of this phenomenon in the specific nature of the Tccnia 

 belonging to the Echinococcus multUocularis, but, except the peculiar geographical distri- 

 bution, he can urge nothing in support of this view beyond the fact that the feeding 

 experiments which he made with the multilocular Echinococcus yielded no positive results 

 (loc. cit., p. 37). 



2 Krabbe, Archivf. pathol Anat., loc. cit., p. 232. 



