TRICHINELLA SPIRALIS 313 



trichinellae have been artificially introduced into the dog, the mole 

 (Talpa europcea), the mouse (Mus musculus), the hare (Lepus 

 timidus), the rabbit (Lepus caniculus), the hedge-hog (Erinaceus 

 europaeus), the marmot (Cricetus vulgaris), the sheep, the calf, the 

 horse, &c. Human beings and the pig, rat, mouse, guinea-pig and 

 rabbit are very easily infected ; less easily the sheep, calf and horse ; 

 with more difficulty the cat, dog and badger. Trichinella can 

 also be reared in birds (fowl, pigeon and duck). However, the 

 young cannot be induced to settle in the muscular system, but 

 are expelled with the faeces. By cold-blooded animals as well as 

 by insects (Calliphora vomitaria) encysted trichinellae are evacuated 

 without undergoing any change, but they will still develop if 

 subsequently ingested, say, by rabbits. According to Gujon, how- 

 ever, trichinella can develop in salamanders, because the same has 

 found trichinella of the muscles in these animals, after they had 

 been fed on encysted specimens. A high temperature (30 C.) 

 must be provided in which to keep the experimental animals 

 to ensure the success of the infection. 



History. Encapsulated trichinellae had already been observed in London by 

 Peacock (1828), and by J. Hilton (1833), i* 1 tne muscular system of man ; soon 

 after (1835) Paget found them in London in an Italian who had died of 

 tuberculosis, and recognised them to be encysted entozoa, which R. Owen 

 described as Trichina spiralis. Soon after some further observations were 

 reported on the occurrence of encysted trichinellae in man in England, 

 Berlin, Heidelberg, Denmark, N. America ; they were also found in the 

 pig (Leidy, Philadelphia) and the cat (Herbst, Gottingen, and Gurlt, Berlin). 

 Herbst even succeeded in infecting a badger with encysted trichinellae and 

 subsequently infected two dogs with the flesh of this badger (1850). In 

 1855 R. Leuckart (Giessen) also commenced feeding experiments, and, like 

 Kuchenmeister and Virchow (1859), first went on the wrong track because 

 it was believed at that time that trichinellae were the larvae either of Tricho- 

 cephalus or Strongylus. Nevertheless, these experiments yielded some im- 

 portant results ; they showed that trichinellae become adult in the intestine 

 within a few days, and that the females are viviparous (Leuckart). 

 Until that time trichinellae had been regarded as fairly harmless guests 

 of man, but opinions soon changed when Zenker in Dresden (January, 

 1860), in performing the autopsy of a io-y ear-old girl who had entered 

 the hospital with typhoid symptoms and there died, found trichinellae (not 

 yet encysted) in the muscles ; the intestinal lesions characteristic of 

 typhoid were lacking, but numerous adult trichinellae were found in the 

 intestine. Enquiries elicited the fact that at about Christmas-time the 

 girl had been taken ill after eating pork, and at the same time the 

 butcher from whom the meat was bought as well as several of his 

 customers fell sick ; the pickled pieces of the same meat were fuil of 

 trichinellae. In the face of this information it was not difficult to 

 ascertain the cause of the disease and the manner of infection in 

 Zenker's case, and it was not long before Leuckart, Virchow and Zenker 



