422 Veterinary Medicine. 



canal is divided into three parts : the anterior (oesophagean) tri- 

 angular on transverse section ; the median covered with nuclea- 

 ted cells which give a peculiar beaded appearance is the small 

 intestine ; and the posterior, narrow and muscular, is the rectum. 



The trichina is viviparous, the fecundated ova hatching out in 

 the body of the uterus, and the escaping embryos making their 

 way into the vagina, to pass out by the vulva. The embryo is 90 

 to 100 fx. long, by 6 /u. in its median and thickest part. 



The larval or muscle trichina is about i mm. long by 40 /* 

 broad, narrowed toward the cephalic end, furnished with an 

 alimentary canal in three parts as in the mature, but with a simple 

 tube only representing the undeveloped sexual organs. These 

 are found at first free, and later in lozenge-shaped cysts, among 

 the muscular fasiculi, in the intermuscular connective tissue and 

 more rarely in the adipose tissue or intestinal walls. 



History. Calcified trichina cysts were noticed by Peacock in 

 1828, and the muscle preserved in Guy's Hospital, London. Hil- 

 ton recorded similar appearances in the muscles of a man of 70, 

 in 1832. Tiedemann had found minute calcified capsules in a 

 gouty subject as early as 1821 but the description makes them too 

 large, and unless there was a mistake in measurement they can- 

 not be accepted as genuine. For the first time in 1834, Paget saw 

 and described the worm rolled up in its cap,sule, and a year later 

 Richard Owen described and named the parasite. Herbst (1850) 

 developed muscle trichinosis in animals by feeding trichinous 

 flesh. Virchow and I,euckart (1859) fed trichinous flesh to dog 

 and pig respectively and claimed to have found the mature 

 trichinae in the bowels, but to Zenker belongs the credit of trac- 

 ing the cycle of life of the worm and its pathogenic action on its 

 host. He traced an attack of trichinosis in a woman to the tri- 

 chinous pork she had eaten, and feeding the infested pork to 

 various mammals, produced trichinosis in each. He demonstrated 

 the young worms in migration, and that they caused a deadly 

 disease in man. 



Geographical Distribution. Trichina has been found in every 

 country in which they have been sought for. They appear to be 

 more prevalent in particular countries and districts, as in Ger- 

 many and the western states of America, but this impression 

 comes largely from the more careful pork inspection in these 



