DEVELOPMENT OF ASCAPJDES. 317 



or a self-infection, analogous to the infection of the sufferers from 

 tapeworm with Cysticerci {Trichina spiralis). 



4. In the examination of the question how we become in- 

 fected with the different species of Strongylus, I find myself 

 totally without data. I mentioned at the time, in Virchow and 

 Reinhardt's ' Archiv./ that I had found in nodules of the lungs of 

 the sheep the young of a nematode worm, which was probably 

 that of a Strongylus, although I have not hitherto known how to 

 apply this fact to the advancement of the question of the pro- 

 duction of the species of Strongylus in the human body, especially 

 those which occur in the kidneys or in the lungs. 



5. With regard to the production of Ascaris lumbricoides also, 

 we are destitute of any certain knowledge. " In Europe," says 

 Bilharz, 1. c., " as far as I remember, they ascribe the Ascarides 

 and Oxyuri to bad flour and bread ; and in Egypt the common 

 people, who feed principally on vegetables, and indeed for the 

 most part on raw leaves and roots, are especially troubled with 

 round-worms," whilst, for instance, in Egypt, the use of raw meat 

 is correctly enough set down as being the cause of the production 

 of tapeworm. How far this supposition is correct, or how far the 

 infection in this case also is produced by the consumption of 

 animal substances, is a question which still needs a close exa- 

 mination. Thus we might suppose, that small snails, caterpillars, 

 larvae of insects, or small beetles and mature insects, may adhere 

 to the leaves and roots which are eaten raw, and which creatures may 

 harbour the progeny of round-worms, most probably in the encysted 

 state. They thus get accidentally into the human intestinal canal 

 with the raw leaves and roots, and there acquire a higher develop- 

 ment. These worms would consequently reach man as a herbivorous 

 animal, but only in the above-described, indirect, accidental way. 

 In the aetiology of the Ascarides, we must not forget, that the 

 localities in which they most generally occur, are usually moist 

 low grounds. Thus the valleys of the Nile, in Egypt, as also the 

 provinces Smaland, Halland, and Schonen, in Sweden, are favorite 

 districts of the Ascarides, and are peculiarly moist coast districts. 

 They are also found in German}', in the neighbourhood of Zittau, 

 which is exposed to the overflowings of the Neisse and Maudan, 

 and in the vicinity of Glauchan (according to communications from 

 Dr. Pause), which is subject to be overflowed by the Mulde. 

 We have now, however, said all that can call for our attention 

 here at present, and I only mention as a matter of curiosity that 



