I20 ELEMENTS OF yiPPUED MICROSCOPY. 



8. Tho Microscopic Examination of Pork for Trichina. 



— The disease known as trichinosis is. hke diphtheria and 

 typhoid fever caused by a parasitic micro-organism, 

 although the parasite belongs to a very different group. 

 Trichina is a minute worm, barely visible as a. speck to the 

 naked eye, which bores its way into the muscles of swine 

 and there encysts itself in a calcareous nodule. If such pork 

 be eaten, imperfectly cooked, the limy cyst is dissolved; 

 the worms emerge and reproduce, and a myriad of their 

 progeny penetrate the tissues of the body, causing high 

 fever and, sometimes death. If the patient recovers from 

 this crisis, the worms encyst themselves in the muscles 

 and produce no further serious difficulty. 



In America, trichinosis is rare in man, although some 

 2% of swine are affected with it, because pork is more 

 or less thoroughly cooked before eating. In Europe, 

 however, where pork products are eaten almost raw, the 

 danger is serious and must be met by preventing the 

 distribution of trichinous swine flesh. Elaborate govern- 

 ment systems of meat inspection have been instituted in 

 many countries; in Prussia, for example, over 25,000 

 officials are employed for this purpose. In the United 

 States the Department of Agriculture for some years 

 maintained a bureau of meat inspection which examined 

 all pork intended for foreign export and interstate com- 

 merce, employing a large corps of microscopists. 



Samples of pork to be examined for Trichina are taken 

 from the diaphragm or other muscles and cut in pieces 

 about an inch by half an inch in size. One such piece 

 is then placed between two slides of heavy glass, mounted 



