210 



LOWER ifrVERTEBRATES. 



Fig. 196. — Trichina 

 spiralis encysted in 

 muscle. 



the discharge of the ulcer serves to set free the brood of young, but the history of 

 the species has not yet been further elucidated. 



The Teichotkachelid^ include the most dangerous by far of human parasites, the 

 one which most often and most rapidly proves fatal to the life of its host, the much- 

 feared trichina. The worm occurs in little distinct capsules in the muscles of the 

 body of many animals ; now when some of the infested muscles of one animal 

 is eaten by another, the capsule is dissolved by the action of the digestive juices, and 

 the larval worms are liberated in the intestines of their new host, where in the course 

 of a week they become mature and then produce millions of eggs, which soon hatch 

 out minute larvae. The larvae shortly penetrate the walls of the intestine and wander 

 about through all parts of the body, injuring and irritating all the 

 tissues they traverse. Finally they settle down in the muscles, 

 penetrate the muscular fibres, feed on the substance thereof, and 

 grow in a few weeks to several times their original size. While 

 wandering and growing they produce the most serious consequences 

 in the health of the host, and being often present literally in millions, 

 the accumulated effects of all the slight injuries i)roduced by each 

 trichina cause the greatest suffering to. their victim, and often lead 

 to his death within a few weeks. Still the host may be restored to 

 good health if ho can survive the first few weeks of danger; for 

 after the trichinae are established in the muscle fibres and have 

 finished their growth, there they remain for years and years, en- 

 closed in tough capsules, in which they lie coiled in a spiral. In 

 this state they produce no serious injur}', and, as after the first attacks are over, and 

 the inflammation they cause has subsided, the muscles and other injured tissues of the 

 host are regenerated, there may be a complete recovery, after passing through the first 

 period of danger. 



Pigs, from their omnivorous habits, are peculiarly exposed to the attacks of tri- 

 chinae. In some German towns it was found that one pig in every three hundred or 

 even less was infested; now such a pig slaughtered and made into sausages and 

 uncooked ham has often served to feed nearly a whole German village, and thus to 

 cause a veritable epidemic of trichinosis. In 1884, shortly after the exclusion of 

 American pork from German)', ostensibly because of the danger of trichinae, there 

 occurred one of the most frightful epidemics just in the manner told above. From 

 one pig the parasites were conveyed to three hundred and sixtj'-one known persons, of 

 whom no less than fifty-seven died within four weeks. This was in the villages around 

 Emersleben, Saxony, having only about sixteen hundred inhabitants. Such outbreaks 

 have been by no means uncommon in Germany, owing to the habit universal there of 

 eating raw or imperfectly cooked meat. To every prudent 

 person it has become an inviolable rule, never to eat any 

 sausage, pork, or ham, which has not been very thoroughly 

 cooked, so that any encapsuled trichinae in the meat may 

 have been killed by the heat. 



The trichinae are found in the muscles in immense num- 

 bers, and often closely crowded together, each worm looks 

 like a coiled hair, whence the name Trichina spiralis. 

 The oval capsules are not over a fortieth of an inch in length, while the worm 

 of course is very much smaller, and always coiled. They were first found by Hil- 



FlG. 197. — Trichina spiralis. 



