48 NATURAL HISTORY SOCIETY OP DUELIN. 



There are, then, some grounds for considering the rahhits on which 

 the Boa was fed to have been concerned in the production of the cestoid 

 worms found in its duodenum, but it is not so easy to conjecture about the. 

 genesis of theAscarides also found in this animal and in the Alligator, for in 

 the present times our knowledge of the development of the jointed worms 

 is much in advance of that of the nematoid parasites. The observations 

 on worms of this latter class have been chiefly made on those which ex- 

 ist in the human body, and these find an entrance into man in two 

 ways; for it appears as if the immigration of at least some of the round 

 worms inhabiting the human intestines takes place in the same manner 

 as that of Tcenia solium, by the use of flesh impregnated with the 

 immature germs of the round worms in question, while the immigration 

 of those which occur in the muscles is sometimes direct and from the 

 outside ; * the latter is the case with the Filaria medinensis, or Guinea- 

 worm. The former is the mode of entrance adopted by the Tricocepha- 

 lus dispar, which is sheltered in almost every human creature, some- 

 times to the number of 1,000 (Rudolphi), and has been found in 

 twenty-six out of twenty-nine cases in which it was looked for. This 

 worm is derived from " trichinous pork," or pork infested with the en- 

 cysted worm called Trichinis affinis by its discoverer, Leidy, of Phila- 

 delphia, in the same way as the common tape-worm is derived from 

 another encysted worm of the pig, the Cysticercus celhdosa. It was 

 formerly believed that the germs of the Filaria medinensis were intro- 

 duced by the mouth, and had some connexion with the quality of water 

 drunk; and among those who live where this worm is endemic this belief 

 still prevails, so that many precautions are taken against swallowing the 

 eggs; the negroes of Schendi strain the water through linen before 

 drinking, and in Guinea, water is eschewed as an unwholesome beverage. 

 These views have been proved to be erroneous, as in the case of a Dutch 

 general in Angola, who ate and drank nothing but food and beverages 

 brought with him from Europe, but yet got the Guinea worm; and a com- 

 panion of Jacquin, when in Curacao, did not drink a drop of water (which 

 Kuchenmeister remarks was not very hard on him, as he was a lover 

 of spirituous liquids), yet he was attacked by the worm, while Jacquin, 

 who drank much water, remained free from it. There are many facts 

 which seem to countenance the opinion that the worm is introduced 

 through the skin ; that in places where the worm is endemic the young- 

 est brood, living free in water, damp grass, or moist soil, gets on un- 

 covered parts of the body, and thence into the interior. The Filaria has 

 been observed by Pruner to live specially in the feet of carnivorous 

 animals, such as dogs and gulls, and rarely in the herbivora. It has not 

 yet been proved that the water and wading birds are attacked. f The 

 backs of the water-carriers in Bengal are often the seat selected by this 



Kuchenmeister, op. cat, vol. i., p. 316. f lb. p. 406. 



