LECTURE XII. 



Prevalence of the Seatworm DiseaseThe Children's Pest Wide 

 distribution of Oxyuris vermicularis The Eggs and their con- 

 tained Embryos Development of the Larvee Opinions of Vix, 

 Leuckart, Zenker, and Heller^-Head-quarters of the Adult 

 Worm Symptoms produced in the Human Eearer. 



GENTLEMEN, The particular parasitic disorder, or 

 helminthiasis, to which I now propose to call your 

 attention, constitutes one of the most prevalent and 

 obnoxious maladies with which we have to deal. 

 Five out of every six persons who come to you 

 stating that they are troubled with worms, wish you 

 to understand that they are infested with Ascarides 

 or, more properly, Oxyurides. Some persons inno- 

 cently suppose that there are but two kinds of human 

 entozoa, namely, threadworms and tapeworms ; and 

 they are not a little surprised when you inform 

 them that all mankind are liable to be invaded by 

 one or other of at least a score of distinct specific 

 forms of helminth. As a rule, however, it is better 

 to withhold this sort of information, for in the case 

 of nervous and apprehensive persons your commu- 

 nicativeness might induce serious mischief. 



