SOME INHABITANTS OF MAN 137 



which the Philistines returned with the Ark of the Covenant 

 reveal still to the understanding mind the intimate association 

 of rats with bubonic plague. 



The Mosaic injunction against the use of certain animals as 

 " unclean " was apparently rightly based upon the fact that 

 these food-animals harbour " cystic " worms in their tissues, 

 some of which, as we shall see shortly, have been proved to be 

 the infective stages of tapeworms in man. Tapeworms were 

 well known to Hippocrates, for he describes a case in which 

 considerable lengths of worm were seen to leave the body. 

 The animal nature of the " hydatids " or cystic worms was 

 clearly suspected in the Middle Ages. 



For long the peculiarly repulsive disease of the tropics 

 called elephantiasis was confused with leprosy, but as early 

 as A.D. 1037 Avicenna clearly distinguished the " Elephanti- 

 asis of the Arabs," which Sir Patrick Manson has shown to 

 be associated with the presence in the lymphatics of a thread- 

 like worm, from " Elephantiasis Graecorum," the true bacillary 

 leprosy. 



Thus the presence of living worms, often incapable of 

 movement and in some of the most inaccessible organs of the 

 body, has always been a source of interest and mystery to 

 physicians and naturalists alike. Throughout the Middle 

 Ages it was universally believed that they originated spontane- 

 ously within the body, and discussion was confined simply to 

 the particular manner in which this " spontaneous generation " 

 came about. By some it was maintained that the worms 

 " arose " from ill-digested food in the alimentary canal or 

 from the secretions of the digestive glands ; others held that 

 they originated from the blood and from " corrupt juices " 

 in various organs of the body. It was much disputed whether 

 the first impulse of creation was due to fermentation or 

 putrefaction or to a special organising principle. 



Even as late as 1853 we find the following opinion : "In 

 the predisposition to worms the thick mucus of the intestine 

 comes under our consideration. From a portion of the 

 mucus the worms are produced by spontaneous generation 

 with the assistance of Asthenia and Dynamia " ! 



