1862.] DR. T. S. COBBOLD ON HUMAN ENTOZOA. 295 



fectly understood. Tt is well known that quantities of the immature 

 ova are expelled their "host" per anum; and I have myself ob- 

 tained the characteristic eggs from matters ejected by the mouth. 

 Richter's and Davaine's experiments go to prove that, after the ova 

 have escaped passively, they complete their development in open 

 waters ; and it would also appear that an interval of six months 

 must elapse (after their expulsion) before the yelk-segmentation and 

 consequent embryonic formation can take place. In Richter's ex- 

 periment none of the embryos had emerged after the eggs had been 

 in the water for a period of eleven months ; and, in the case of A. 

 marginata from the dog, Verloreu's previous investigations have 

 shown that the young embryos can retain their vitality for more than 

 a year after their worm-like condition has been attained. According 

 to Davaine (Comptes Rendus, 1858, p. 1217), the fully developed 

 embryo is cylindrical, its length y^th of an inch, the mouth is not 

 furnished with the three characteristic papillse of the genus, and 

 the tail terminates suddenly in a point. 



His experiments also showed that their development in ovo was 

 not facilitated by increase of temperature, neither were the mature 

 eggs affected by several days' immersion in the gastric juice of rab- 

 bits and dogs. Further researches therefore are required to decide 

 whether the young Ascarides eventually gain access to our bodies 

 after the embryos have escaped from the eggs and have undergone 

 a series of active wanderings elsewhere, or whether, as seems more 

 probable, they are not directly transferred from river- and pond- 

 water to the human stomach. 



11. AscARis MYSTAX, Rudolphi. 



A. mystax, Rudolphi, Bremser, Gurlt, Dujardin, Bellingham, Die- 

 sing, Siebold, Nelson, Allen Thomson, Meissner, Kolliker, Bischoff, 

 Leuckart, Claparede, Cobbold, &c. 



A.felis, Gmelin, Frohlich, Rudolphi, J. V. Thomson, Pickells. 



A. teres felis, Goeze. 



A. cati, Schrank. 



A. alata, Bellingham, Dujardin, Diesing. 



Fusaria mystax, Zeder. 



Although no one has hitherto regarded the Ascaris mystax as a 

 human parasite, I am satisfied that Bellingham's Ascaris alata 

 (about which there has been so much dispute) is neither more nor 

 less than the well-known A. mystax of the Cat. But if this be 

 doubted by Continental helminthologists, I invite their attention to 

 evidence which, to any one conversant with the characters of Ascaris 

 mystax, cannot fail to satisfy them that this nematode is liable to 

 infest the human body. The first instance in which this parasite 

 has been observed in man is recorded by Dr. Pickells in the ' Trans- 

 actions of the Association of Fellows and Licentiates of the King 

 and Queen's College of Physicians in Ireland.' The case is reported 

 at length in vol. iv. pp. 189-221, and in vol. v. pp. 171-196, the 

 text being accompanied by figures of a nematode unmistakeably re- 



