110 



THE HELMINTHES. 



§ 104. 



The central nervous system of the Acanthocephali is very distinct. It is 

 always concealed at the bottom of the sheath of the proboscis, which this* 

 last, being never in a state of complete retraction, does not fill. It consists 

 of a dense mass of ganglionic, cellular globules blended together, and here 

 and there may be seen through the cell-membranes their nuclei and corpus- 

 cles. This comparatively large mass sends ofi" nerves in every direction, but 

 the tenuity of these prevents their being traced, especially after they have 

 entered the muscular walls of the proboscideal sheath.'^' 



With the Gordiacei,^'"* and Nematodes, a nervous system has been found 

 with certainty only in Strongylus gigas. Here a cord arises from a swell- 

 ing in the head, traverses the whole length of the body upon the median 

 ventral line, and terminates at the posterior end of the body in another 

 swelling. It sends off in its course lateral filaments, thus resembling the 

 nervous system of the Sipunculidae.*'^* 



4 I have thus found the nervous system of the 

 Acanthocephali ni Echinorhyncus gigas, angus- 

 tatus, haeruca, ami proteus. It can be easily ob- 

 served by carefully pressmg or tearing the probos- 

 cideal sheath. In thus tearing, you sometimes 

 completely expose , the ganglionic mass with the 

 roots of the nerves. In no species that I have dis- 

 sected have I been able to find the ganglionic ring 

 mentioned by Henlc (FroriejPs neue Not. No. 

 285, p. 330, and MiMer''s Arch. 1840, p. 318) as 

 found about the genital orifice of Echinorhyncus 

 nodulosus. 



Dujardin also (Hist. Nat. d. Helm. p. 49.5, 491, 

 PI. VII. fig. D. 4), has not observed it, but he dis- 

 tinctly perceived the central mass at the base of 

 the proboscis, and has figured and named it as un 

 corps glanduleux on ganglionaire. 



•' As yet no nervous system has been found in 

 the Gordiaoei. Berthold (Tiber den Bau des Gor- 

 dius aquaticus, 1842, p. 12) has been incUned to 

 regard as nerves two delicate filaments which 

 traverse the cavity of the body of Gordius ; but, 

 as these give oS no lateral branches, this opinion 

 cannot be admitted.* 



6 Many Hehninthologists have erroneously taken 

 for nerves the deUcate projecting lines which, situ- 



ated directly subcutaneous and often blended with 

 the skin, traverse the whole length of the body of 

 many Nematodes, and have been called the ventral 

 and dorsal lines. Their lateral branches, as already 

 observed, are only transverse muscular bands. 

 Quite different from these is the longitudinal cord, 

 which Otto (Magaz. d. Gesellch. naturf. Freunde 

 zu Berlin, 7ti» Jahrg. 1816, p. 225, Taf. V.) has 

 described and figured as belonging to the nervous 

 system ; a view which I am disposed to adopt, in 

 spite of Nitzsch {Ersch and Gruber''s Encyclop. 

 VI. 1821, p. 45) and other Helminthologists. 



In a large female Strongylus gigas, now under 

 my eyes, there is a simple longitudmal cord beneath 

 the muscular envelope, and therefore in direct con- 

 nection with the skin, and which extends along 

 the ventral surface. In its course it sends off 

 numberless lateral branches, which in their inti- 

 mate structure are quite different from the trans- 

 verse muscular bands. But neither here nor upon 

 the nerves of other worms have I ever seen the 

 enlargements spoken of by Otto. Granfs figure 

 of a double nervous filament traversing the body 

 of Ascaris is probably unaginary ; see Outlines of 

 Comp. Anat. p. 186, fig. 82, A. 



gus, which he regards as a brain ; these observa- 

 tions have since been confirmed by Van Beneden 

 (Ann. d. Sc. Nat. XI. 1849, p. 319), who, however, 

 regards this mass as belonging to the sympathetic 

 system. But, however viewed, an oasophageal col- 

 lar has been distinctly made out, thus confirming 

 the views of Cuvier. 



In regard to the splanchnic system of nerves 

 with these animals, Van Beneden (loc. cit.) de- 

 scribes it as consisting of two ganglia lying on the 

 oesophagus back of the oesophageal collar, and 

 from which pass off two filaments, which run along 

 the oesophagus, and enter the collar laterally. He 

 thinks the two ganglia are united by a transverse 



commissure. Further behind is another and larger 

 ganglion on each side, and fi-om which pass off 

 filaments to the digestive cavity. See also ray note 

 under § 99. — Ed. 



* [ § 104, note 5.] This view of Berthold is sup- 

 ported also by Blanchard (Ann. d. Sc. Nat. 1849, 

 XII. p. 6), who affirms that he has observed on 

 both sides of the body a double longitudinal cord, 

 which is usually very distinct. This, examined 

 microscopically, appeared to be composed like the 

 nerves of the other Helminthes. Blanchard, how- 

 ever, did not succeed in tracing these cords to any 

 cephalic centres. Nothing of special value, there- 

 fore, is known on this subject. — Ed. 



