TRANSMISSION OF DISEASE FROM ANIMALS 29 



tion. The main points in connection with trichiniasis 

 are: — 



1. The persistence in a Hving form of the hirvfje 

 of the parasite for considerable periods in the flesh 

 of the affected animals, like swine. 



2. When such meat is ingested the larvae are 

 liberated in the intestines and then commence to 

 multiply and migrate, and the disturbance produced 

 in the body of man by their acti\'ity giv^es rise to 

 the symptoms characteristic of tricliiniasis, such as 

 fev^er, etc., etc. 



3. The pig infected man, man infected the rat, and 

 the rat infected the pig. 



During the same period our knowledge of the 

 other intestinal-worm diseases advanced, and the re- 

 lationship of the phases of the parasites living in the 

 animal to those living in man was worked out. For 

 example, Tienia ecJmiococcus inhabits the dog, the dog 

 infects man through the eggs of the ttenia infecting 

 the food of man ; the eggs, when swallowed, develop 

 in man into the scolex or hydatid phase, and there are 

 many more examples. 



The next great step was made when the relationship 

 of the guinea worm to man, and to the minute 

 crustacean Cyclops was demonstrated by Fedschenko 

 and Leuckart. It was proved that the larvae of the 

 mature guinea worm upon reaching water were taken 

 up by the cy clops. Now if water containing these 

 infected cyclops was consumed by man, the parasites 

 were liberated in the stomach of man and from thence 

 migrated to the subcutaneous tissues where the adult 



