NEMATOIDEA. . 407 



lunger than the body, which communicates witli a (sometimes double) 

 penis that protrud(^s through the anus. The latter opens under the 

 extremity of the tail. 



Two Avhite threads, one of which extends along the back, and tlie 

 other along the belly, are considered by Messrs Otto and Cloquet as 

 tlie nervous system of these animals ; two other and thicker threads, 

 one on the right and the other on the left, are considered by some as 

 muscular, and by others as vascular, or even as trachetie. 



In some, the head is destitute of lateral membranes. The most 

 common species. 



A. lumbricoMes, L., is found without any essential difference 

 in Man, the Horse, Ass, Zebra, Hemiona, Ox and Hog. It has 

 been seen more than fifteen inches in length. Its natural colour 

 is white, and it sometimes multiplies excessively, occasioning 

 disease and death, particularly in children, or when it ascends 

 into the stomach. 

 Other species are furnished Avith a little membrane on each side 

 of the head. Such is 



A. verviicularis, L. ; Gcetz., V, 1 — 6 ; Encyc. Method., Vers, 

 XXX, pi. X, 1. Very common in children, and in adults af- 

 flicted with certain diseases, in which it causes an insupportable 

 itching at the anus. It is not more than five lines in length, and 

 is thickest anteriorly*. 



Strongylus, Mi'iLf, 



Where the body is roimd, and the anus of the male is enveloped by 

 a sort of bursa, variously shaped, from which issues a little thread 

 that appears to be an organ of generation. These two last characters 

 are wanting in the female, which has sometimes caused her to be 

 taken for an Ascaris. 



In some of these Strongyli the mouth is ciliate or dentated. Such is 



5. equinus, Gm. ; St7\ armatus, Rud. ; Miill., Zool. Dan., II, 



xlii ; Encyc. Method., XXXVI, 7 — 15. Two inches in length ; 



head hard and spherical, and the mouth surrounded by small, 



soft spines ; bursa of the male trifoliate. Of all the Worms that 



infest the Horse, this is the most common ; it even penetrates into 



the arteries, where it occasions aneurisms. It is also found in ihe 



Ass and Mule. 



The mouth of others is merely surrounded by tubercles or papillae. 



Such particularly is the 



S. gi(J(is, Rud. ; Ascaris viceralis and yhc. renalis,Gm. ; Redi., 

 An. Viv. in An. Viv., pi. VIII and IX ; Le Dioctophyme, CoUet- 

 ' Meygret, Journ. dePhys., LV, p. 458. The most voluminous of 

 all known intestinal Worms ; it is upwards of two or three feet 

 in length, and as thick as the little finger. The most singular cir- 

 cumstance attending this Strongylus is that it is most usually de- 

 veloped in one of the kidneys of various animals, such as the 



* For the remaining species of Ascarides that infest animals, see Rud., Hist., II, 

 128, et seq. and Synop., p. 37, et seq. 

 t ST/jo/^yXis, round. 



