the Origin of Intestinal JVonm. 348 



more easily proved. The distribution of these two species in 

 different coiintrics cannot arise, as has been already shewn, 

 from difference in diet, manner of life, or climate. The hypo- 

 thesis of a certain German professor, that their different distri- 

 bution might indicate a difference in the races of mankind, is 

 one of the most extraordinary examples possible of predilec- 

 tion for a favourite theory. If any proof against such an opi- 

 nion were wanting, it might be found in the fact, that the negro 

 in the West Indies appears to suffer from Tctnia solium ; a 

 worm of this species, passed by a negro, having been sent me 

 some years ago by Dr Raon of St Thomas. The reason why 

 the negro slave suffers from Taenia is not that his pedigree may 

 be traced from a root common to him and to the Anglo-Saxon, 

 but that from this source he has derived the Taenia, with many 

 other things, good and bad. It would be interesting to know 

 whether the inhabitants of the Russian colonies are subject to 

 the Bothriocephalus. 



It is a well-known fact that Dr Sommerring suffered from 

 a Bothriocephalus latus, and it was by an examination of this 

 specimen that the specific character of this kind of worm was 

 ascertained. When the fact was first known, Sommerring 

 was supposed to belong to a Swiss family, but, as this was not 

 the case, the origin of the worm was ascribed to his residence 

 in Switzerland ; not that his body was so altered in this coun- 

 try as spontaneously to produce a Bothriocephalus instead of 

 a Taenia, nor that the food of the country was so peculiar as 

 to be thus metamorphosed, but merely because an ova or 

 young one of the species was here introduced into the frame. 



A striking example of the inconsistency of human belief is 

 afforded by the opinion generally received in some countries 

 respecting the Filaria medinensis. This species of Filaria has 

 all the characters of an intestinal worm, and still has been 

 supposed to be introduced from without, whilst all the others 

 have been held to arise spontaneously. It is endemical in 

 Guinea, and attacks Europeans as well as negroes. Its pre- 

 sence is not observed for a time, sometimes for a couple of 

 yeare, as was proved by the case of a boy who suffered from 

 this worm at Copenhagen, two years after his departure from 

 Guinea. 



As the view that the Kntozoa multiply like other animaU 



