272 THE ROUND WORMS 



diaphragm and may remain alive as long as ten to twenty years; finally, however, 

 the cyst undergoes calcareous infiltration and the embryo dies. 



When uncoiled the embryo is about i mm. long with the mouth at the attenuated 

 end. Among cannibals it would be easy to keep the cycle going by eating improperly 

 cooked or raw human meat, the parasite being thus transmitted. 



As this would not explain the transmission among civilized men, the 

 following is the life history: Man obtains his infection from eating raw 

 pork, the embryos encysted in the muscle of the hog being liberated in 

 the stomach, and the males and females developing in the intestine as 

 above described. The hog may gain his infection by eating the meat 

 of other hogs or rats. These rats eat scraps of pork at slaughter houses 

 and become infected. Being cannibals, rats when once infected, con- 

 tinue to propagate the infection. In man, during the first two or three 

 days while the adults are breeding in the intestine, we have gastroin- 

 testinal symptoms. 



It is during this period or at any rate before the fifth day that 

 purging may be of benefit. About ten to twenty days after infection 

 the embryos begin to wander and we have the acute muscle pains. 

 In the diagnosis we should try to obtain specimens of the pork which 

 has caused the trouble in order to examine for encysted trichinae, or 

 to feed to white rats or rabbits, subsequently examining the diaphragm 

 of these animals for encysted trichinae or the intestine for adult trichinae. 

 Excision of a small piece of the deltoid of man may confirm the 

 diagnosis. The best method is to take blood in 3% acetic acid, 

 centrifuge, and examine for larvae. 



During the diarrhceal stage we may examine the stools for adult worms, in 

 particular dead males or possibly actively motile embryos these latter are about 

 90X6^. 



Always examine the blood for eosinophilia. 



It is well to remember that the parts of meat which trichinae prefer (muscle of 

 diaphragm, of neck, etc.) are often used in sausage. Unfortunately it is almost 

 impossible to detect the embryos in sausage meat. 



STRONGYLID.E. 



In this family the male has a caudal bursa, a prehensile sort of ex- 

 pansion at the posterior end for copulatory purposes. 



The mouth is usually provided with six papillae and at times with a 

 chitinous armature. Those without the chitinous armature are in- 

 cluded in the subfamily Strongylinae (Strongylus, Trichostrongylus) 



