33 



And if the intruder happens to be a female, with fertilised 

 eggs, these eggs may be easily transferred to the mouth of the 

 individual, who thereby becomes infected in his turn 1 . 



An Obsolete Theory. 



This may be accepted as occurring very occasionally. But 

 the theory of Vix and KUECHENMEISTER, that such a female 

 may deposit eggs in the rectum which may be hatched there, 

 or may creep up higher in the intestine, and there go through 

 a similar process, is no longer defended by any authority. 

 The eggs could not by such means reach the stomach or 

 duodenum, the only places where hatching has been shown 

 to be possible. In any case, wanderings from rectum to rectum 

 must be extremely rare, but there is no reason to doubt that 

 persons living together, and more particularly children, often 

 infect each other in other ways, probably through contamina- 

 tion of fingers, or of clothing, towels and the like, from any 

 of which the eggs may easily be conveyed to the mouth 2 . 



Re-infection. 



When once infection has taken place, re -infection (or as 

 some call it, auto -infection) is the rule, especially in children, 

 as explained above. The modus operandi is as follows : 

 the irritation caused by the worm, particularly during its 

 nocturnal migrations, leads to violent scratching of the anus 

 and perinaeum, often unconsciously, during sleep. By this 

 means, the worms may be broken up and the ova they contain, 

 or those which have already been deposited, are smeared on 

 the fingers and forced under the nails 3 . Thus they may easily 



1 Some authors consider it ad vis- 2 " Perhaps also flies or their 



able, as a prophylactic measure, to excrement play a part in the dis- 



treat the whole of a family, if only tribution of the parasite similar 



one member appears to be affected: to that demonstrated by Grassi as 



" Vielfach haben wir uns iiberzeugt taking place in the spread of the 



dass in kinderreichen Familien oft ova of Trichocephalus and Taenia." 



sammtliche Kinder bis in das (BRATJN, M., The animal parasites 



jiingste Alter, Oxyurenbeherbergen. of man; brought up to date by 



Bei Abtreibungscuren pflegen wir SAMBON, L. W., London, 1906, 



daher alle Familienmitglieder zu pp. 339, 340.) 



beriicksichtigen." (MosLER, F. 3 " Ordinarily, children become 



und PEIPER, E., Thierische Para- infested by biting their nails, be- 



siten in NOTHNAGEL'S Specielle neath the margins of which the eggs 



Pathologie und Therapie, Wien, lie concealed. Professors Heller, 



1894, band vi., p. 228.) Zenker, and myself have, all more 



