230 PARASITES OF MAN 



' Lectures/ it be asked whether the embryos which have 

 escaped into the bowel are capable of arriving at the vermiform 

 stage, the answer is in the affirmative ; for, as Leuckart says, 

 " the elongated embryos are to be found not only in the faeces 

 but also in the mucus of the rectum above and around the anus/' 

 Vix has also asserted that free vermiform embryos are occa- 

 sionally to be detected in the intestine of the human bearer 

 along with the eggs ; this hatching within the lower bowel, 

 however, must, in my opinion, be regarded as exceptional. 

 Heller is of the same opinion. According to Leuckart, the 

 escape of the embryos from the eggs " ordinarily takes place 

 under the action of the gastric juice, also primarily in that 

 condition when they have by some means or other gained 

 access to a new bearer." Prof. Leuckart and three of his 

 pupils courageously infected themselves by swallowing the eggs, 

 and had the satisfaction of observing young Oxyurides in their 

 stools fifteen days afterwards. 



From the united labors of Professors Zenker and Heller it is 

 now rendered certain that all the further changes necessary to 

 bring the larvaa to sexual maturity are accomplished within the 

 small intestines of the human bearer; and it is not necessary 

 that a change of hosts should occur at any time during the life of 

 the parasite. Infection ordinarily takes place by the accidental 

 and direct conveyance of the eggs that are lodged in the neigh- 

 bourhood of the victim's anus to the mouth. Since the victim 

 may accomplish this during sleep, it is not in all cases fair to 

 charge infected persons with uncleanliness. On the other hand, 

 it too often happens that due care in this respect has not been 

 exercised, and from such persons you may remove the eggs of 

 Oxyurides from the margins of the finger nails. One aristo- 

 cratic person, who was infested by myriads of these entozoa, 

 confessed to me that in his extreme distress, and consequent 

 rage, he had freely bitten the live worms in halves between his 

 teeth. He had thus exposed himself to a terrible revenge, 

 since multitudes of the ova entering his mouth subsequently 

 found their way into the stomach and intestines. By whatever 

 mode the eggs are conveyed to the mouth their subsequent 

 passage to the stomach ensures their being hatched. In the 

 duodenum and other divisions of the small intestines, as Zenker 

 and Heller have shown, the embryos undergo transformation, 

 casting their skins, and growing with great rapidity. Probably 

 not more than three weeks or a month is necessary to complete 



