DIAGNOSIS 369 



occasion. The worms may be discovered in the stools. To find 

 the worms, a portion of the feces should be spread on a glass 

 plate or black background and examined with a low power lens. 

 The trichinellae if present will appear as small, glistening, sil- 

 very threads. In doubtful cases the diagnosis may be made by 

 the removal of a small fragment of muscle. A special harpoon 

 has been devised for this purpose by means of which a small 

 portion of the biceps or of the pectoral muscle may be readily 

 removed. Under cocaine anaesthesia an incision may be made 

 and a small fragment removed. Trichinosis may be mistaken 

 for acute rheumatism, particularly as the pains are severe 

 on movement, but there is no special swelling of the joints. 

 There is tenderness in the muscles both on pressure and on 

 movement. The intensity of the gastro-intestinal symptoms 

 in some cases has led to the diagnosis of cholera. Many of 

 the former epidemics were doubtless diagnosed as typhoid 

 fever. The pains in the muscles, swelling, oedema and short- 

 ness of breath are the most important diagnostic points. 



It is practically impossible to diagnose this affection in 

 living swine except by removing bits of infested muscle for 

 microscopic examination. 



§ 299. Prevention. It is not definitely known how 

 swine became diseased. It has been shown by Stiles that they 

 are infested largely from rats about slaughter-houses, which 

 are infested from eating portions of trichinous flesh of swine. 

 It is very likely that hogs fed upon offal become infested. 

 Swine should, as far as possible, be grain fed and not be 

 allowed to eat offal. For the human subject the surest pre- 

 vention is the thorough cooking of all pork and sausages. 



REFERENCES. 



Wii^LiAMS. The frequency of trichiniasis in the United States. 

 Journal of Medical Research. Vol. VI. (1S92). p. 64. 



