vi NEMATODA ASCARIDAE 139 



The tail of the mule is ventrally curved, and usually there are 

 two horny spicules. The Ascaridae are found in the intestines 

 of their respective hosts. 



Genera : Ascaris, Hcterakis, Oxyuris, Nematoxys, Oxysoma, and 

 many others. 



Yon Linstow l enumerates over 250 species of Ascaris, of 

 which it will only be possible to mention here one or two. They 

 are all parasitic in Vertebrata. 



A. luinliricoidcs Linn, is one of the largest known Nematodes 

 (<j = 4-G in., ? = 10-14 in.; Figs. 66 and 67). It is a 

 common parasite in man, and has been found in the ox. It is 

 now generally recognised as the same parasite which inhabits the 

 pig, and which Dujardin regarded as specifically distinct, and 

 named A. suillae. In the latter host, however, it never attains 

 the dimensions it does in man. It inhabits the upper and middle 

 parts of the small intestine, and has been known to escape into 

 the body-cavity and set up abscesses there, or to make its way 

 into the stomach, and to be voided through the mouth. It is 

 practically cosmopolitan in distribution, and is very common in 

 Japan Baely found it in twenty-one out of twenty-three jwst- 

 mortems and in Tonquin and tropical Africa. Heller 2 states that 

 no one is free from these worms in Finland, and they are common 

 wherever there is a plentiful water supply, as in the marshy 

 districts of Holland and Sweden. In Iceland alone they seem 

 absent. When examined alive they give off an irritating 

 vapour which seriously affects some observers, causing catarrhal 

 symptoms, which in Bastian's case lasted six weeks. The 

 usual number found in one host is small, one to six or eight, but 

 cases are on record where many hundreds occurred in one 

 person. 



The details of the life-history of this form are not yet com- 

 pletely worked out. The eggs leave the body of the host with 

 the excreta, and formerly it was thought they re-entered the 

 alimentary canal in drinking-water, etc., and there developed into 

 the adult without change of host. This view has been combated 

 by Leuckart, who failed to rear the Nematodes by direct feeding, 

 and it has been noticed that the youngest parasites found in the 



1 ComjKiuliiDii <lcr HclmintltoJoyic, Hannover, 1S7S, and .Y<n7<<m</, 1389. 



2 A. Heller, " Dannsclmiarotzeu " in v. Liemssen's llundb. d. .?>. 1'itlli. u. Thcr. 

 vol. vii. 



