THE ANIMAL PARASITES OF MAX 



Ml. 



body wall. In many species large stretches of the gut are provided 

 with dilator muscles. There is sometimes a retrogressive absorption 

 of the gut in the adult stage of a few parasitic species. 



INTESTINAL C^ECA and CESOPHAGEAL GLANDS sometimes exist as 



intestinal appendages ; 

 the former are tubular 

 appendages of various 

 size, running backwards 

 Sc. or forwards, and aris- 



ing from the posterior 

 extremity of the oeso- 

 phagus. They are lack- 

 ing in many species. 

 The cesophageal glands 

 are unicellular ; a dorsal 

 and two sub ventral 

 glands may be distin- 

 guished according to 

 their position ; as a rule 

 they open into the 

 oesophagus at a distance 

 from one another. The 



FIG. 262. Transverse section through Ascaris hunbticoides , , /- ,, , , , 



at the level of the oesophagus behind the nerve ring. Cu., bocl Y ol the gland lies 



cuticle; Sc., subcuticular layer; Ex., excretory vessel; Is., ' m the bulb of the O3SO- 

 isolation cell and the system of lamellae proceeding from it ; , ,, , , 



M., muscles; ML, median line ; SI., lateral line. Magnified. pnagUS, Or in the dorsal 



(After Goldschmidt.) Cll \ _ L { c . S(1C arising 



from it. 



THE NERVOUS SYSTEM is sufficiently known in a few species only; 

 it consists of a ring containing fifty to sixty fibres closely surround- 

 ing the oesophagus, various groups of ganglion cells, and a certain 

 number of nerves extending anteriorly as well as posteriorly. The 

 remarkably small number of fibres, as well as ganglion cells, is 

 characteristic of the nervous system of all Nematodes. Immediately 

 behind the cesophageal ring (fig. 263, Lg.) an agglomeration of gan- 

 glion cells lies at either side (lateral ganglia) ; part of their off-shoots 

 form the cesophageal ring, and part are directed posteriorly and 

 ventrally, and unite partly in front of and partly at the back of the 

 excretory pore, with fibres originating direct from the cesophageal 

 ring, and passing along the ventral median line to the back ; these 

 fibres then together form the ventral median nerve (fig. 263, I 7 .///.//.). 

 This nerve, originally consisting of thirty to fifty fibres, becomes 

 in the female attenuated quite evenly in its further course. There is 

 also an agglomeration of ganglion cells close in front of the anus (anal 

 ganglia), and then- the median nerve divides in order to combine with 



