as Enemies of Ma7ikind. 



19 



muscles of mammals and birds. Individuals so infested by the 

 parasite are said to be trichinous ; the common rat, the pig, and 

 man share the unhappy distinction of being the species most 

 frequently infested. While encysted the immature Trichina 

 remain in a state of suspended animation, and are therefore 

 incapable of further development. This inertia, which may last 

 for many years, is only overcome if and when another warm- 

 blooded vertebrate devours a portion of the trichinous flesh. In 

 the course of digestion the gastric juices dissolve the calcareous 

 cysts and the young Trichina emerge in the bowel of their new 

 host. They now^ grow rapidly and perfect their sexual organs. 

 The sexes are distinct, the males being smaller than the females. 

 This development takes three or four days ; within a week the 

 Trichina are fully adult, and pairing takes place. The females 

 carry enormous numbers of ova (1,000 to 15,000) ; after fertilization 

 these develop and are hatched within the body of the mother, 

 the young being eventually brought forth alive. Young Trichina 

 begin to appear in the intestine at about the eighth day after 

 infection ; they at once migrate by perforating the walls of the 

 alimentary canal and the abdominal cavity, and so find their way 

 into the muscular tissue, where they encyst themselves. The 

 migration takes about ten days, and the encystment commences 

 in about fourteen days. Each young Trichina, as a rule, forms 

 its own cyst ; but sometimes cysts containing two, very rarely 

 even three, of the worms are found. 



Such is what may be termed the normal life-history of this 

 parasite; but of the large numbers sometimes liberated in the 

 bowel on infection, and of the enormous numbers born subsequently, 

 a certain proportion usually escape from the alimentary canal of 

 the new host with the faeces. An animal feeding upon such 

 trichinous excrement will also be infected. 



Man is infected by eating trichinous pork, particularly when 

 raw or only partially cooked. In spite of microscopic examination 

 of carcases, it is impossible in practice to guarantee that any given 

 pig is absolutely free from encysted Trichina, and as a matter of 

 precaution every particle of pork should be thoroughly cooked 

 before being eaten. No less than 32 per cent, of the German 

 cases, between 1881 and 1898, were traced to pork officially in- 

 spected and passed as being free from this parasite. Trichinosis 

 in man is a very serious malady. Infection is followed by nausea, 

 loss of appetite, diarrhoea, and fever ; later, when the young 



