1862.] DR. T. 8. COBBOLD ON HUMAN ENTOZOA. 295 
fectly understood. It 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 4. 
marginata from the dog, Verloren’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 ;+>th of an inch, the mouth is not 
furnished with the three characteristic papille 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. mystaz, Rudolphi, Bremser, Gurlt, Dujardin, Bellingham, Die- 
sing, Siebold, Nelson, Allen Thomson, Meissner, Kolliker, Bischoff, 
Leuckart, Claparéde, Cobbold, &c. 
A, felis, Gmelin, Fréhlich, 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- 
