14 



III. THE THREADWORM IN ZOOLOGY. 



The threadworm has suffered many vicissitudes at the 

 hands of zoologists of all times, and even to this day its exact 

 biological status is by no means firmly established. But, 

 technicalities apart, three broad phases may be distinguished 

 in the history of the threadworm. They are marked off by 

 the answers given, in each period, to two main questions 

 which could not fail to present themselves to observers : 

 (1) How, and where, does the worm originate ? and (2) Is its 

 presence in the human body an essential condition of its life, 

 or a mere incident ? 



The First Phase : 



In the first phase, the parasite was thought to arise de novo 

 in the human faeces, as the product of decomposition 1 , which 

 might take place either in the intestine or outside 2 . Such an 

 origin, known as generatio equivoca 3 , or " spontaneous genera- 

 tion/' was attributed to many of the lower animals, and this 

 view held the field down to comparatively recent times. In the 

 light of present-day knowledge, it seems, at the first glance, 

 difficult to believe that scientists ever accepted such a theory. 

 The comparatively high development and great specialisation 

 of the organs of Oxyuris prove to us that the species must have 

 gone through a period of evolution extending over countless 

 generations ; and the idea of so highly organised a creature 

 springing into existence out of nothing, as it were, would 

 appear preposterous to the most elementary student of modern 



1 Oxyuris was supposed to spring 3 Some authors credit Egypt 

 from decomposing milk : " Circa with being the birthplace of the 

 quae vermium genera notandum, hypothesis of spontaneous gene- 

 quod parvitenues ex lactis prae- ration : " Die unziihliche Menge 

 cipue corruptione generari possint." von Mausen, die bei ihnen (i.e., 

 (EYSSEL/M. A., De febre infantum den Egyptern) gemeiniglich nach 

 putrida, Erfurti, 1693, p. 11.) der Ueberschwemmung des Nil- 



2 " Veteres medici vermes intes- flussss durch die Sonnenhitze aus 

 tinales ex putredine, seu ex materia dem Schlam ausgebriitet wurden, 

 spissa caloris atque motus intestini konnte ihnen zu dieser Meinung 

 ope nasici, arbitratisunt." (HiNZE, leicht Gelegenheit geben." (KRAT- 

 P. E., De febris . . . Verminosis, ZENSTEIN, C. G.. op. cit., pp. 

 Helmstadii, 1780, p. 7.) 6, 7.) 



