30 THE DISEASES OF DOMESTIC ANIMALS. 



Notwithstanding the apparent negation of the quoted Berlin 

 experiments, we have the very highest authorities affirming, on the 

 strength of positive observations, that intestinal and embryonal 

 trichmcB do leave the invaded organism with thefceces. 



Leuckart says : " As the usually matured trichinae accumulate in 

 great numbers in the intestines, and as the irritation caused by 

 them leads to the development of a more or less intense diarrhoea, 

 it is evident that the young must be taken up and pass off with the 

 faeces ; and not only free embryos, but also pregnant females, are 

 subjected to this removal, which has been sufficiently attested by 

 my own observations and those of Vogel, Kuhn, Gerlach, and 

 others. This form of migration, under favorable circumstances, 

 also contributes to the further distribution of trichinae. Haubner 

 and Gerlach give cases where they intentionally caused the invasion 

 of young — non-infected — swine by causing them to live in the same 

 pens with known infected ones. Such embryos and pregnant fe- 

 males become mixed with the manure and bedding of the hog-pens 

 or on the grass of pastures, and may be taken up by other swine, or 

 even by the original autosites, thereby leading to renewed inva- 

 sion. 



In the above we have a course of invasion in which the swine 

 are the only factors. 



Is there no other factor (or factors) in the question ? We have 

 previously remarked that wild swine have been found trichinous ; 

 also that rats, dogs, foxes, and other wild animals serve as autosites 

 to them. 



Of all animals in which these parasites have been found, none 

 have that interest, aside from swine, to the hygienist and patholo- 

 gist which is enjoyed by the rat, on account of a hypothetical etio- 

 logical connection between the trichinae which infest them and 

 those in swine. 



Leisering appears to have been the originator of this hypothesis. 



The following statistics will suffice to show that the rat is even 

 more favored with trichuriasis than swine : 



Of 704 rats from different parts of Germany, 59 were found 

 trichinous — 8*3 per cent. 



Of 208 rats from German knackers, 46 were found trichinous — 

 22*1 per cent. 



Of 224 rats from German slaughter-houses, 12 were found tri- 

 chinous — 6 per cent. 



Of 272 rats from other places, 1 was found trichinous — 0*3 per 

 cent. 



