ENTOZOA. 



135 



gus (b,fig. 95) is round and slightly contorted, 

 and suddenly dilates at the distance of about two 

 inches from the mouth into the intestinal canal; 

 there is no gastric portion marked off in this 

 canal by an inferior constriction, but it is conti- 

 nued of uniform structure, slightly enlarging 

 in diameter to the anus. The chief pecu- 

 liarity of the intestine in this species is that 

 it is a square and not a cylindrical tube, and 

 the mesenteric processes pass from the four 

 longitudinal and nearly equidistant angles 

 of the intestine to the abdominal parietes. 

 These processes, when viewed by a high mag- 

 nifying power, are partly composed of fibres 

 and partly of strings of clear globules, which 

 appear like moniliform vessels turning around 

 the fibres. The whole inner surface of the 

 abdominal cavity is beset with soft, short, 

 obtuse, pulpy processes, which probably im- 

 bibe the nutriment exuded from the intestine 

 into the general cavity of the body, and carry 

 it to the four longitudinal vessels, which tra- 

 verse at equal distances the muscular parietes. 

 The analogous processes are more highly de- 

 veloped in the Ascaris lumbricoides, in which 

 species we shall consider the digestive and 

 nutritive apparatus more in detail. 



The mouth (d, fig. 87 and fig. 85) is sur- 

 rounded with three tubercles, of which one is 

 superior (, fig. 85), the others inferior (6, 6) ; 

 they are rounded externally, triangular inter- 

 nally, and slightly granulated on the opposed 

 surfaces which form the boundaries of the oral 

 aperture (c). The longitudinal muscles of the 

 body are attached to these tubercles; the dorsal 

 fasciculus converges to a point to be inserted 

 into the superior one ; the ventral fasciculus 

 contracts and then divides to be inserted into 

 the two which are situated below. By means of 

 these attachments the lon- 

 gitudinal muscles serve to 

 produce the divarication of 

 the tubercles and the open- 

 ing of the mouth ; the tu- 

 bercles are approximated by 

 the action of a sphincter 

 muscle. 



The oesophagus (e,fig. 

 Head and mouth of 87) is muscular and four 

 Ascaris lumbricoides. or five lines in length, nar- 

 row, slightly dilated pos- 

 teriorly, and attached to the muscular pa- 



Fig. 86. 



Fig. 85. 



Transverse sectwn of Ascaris lumbricoides, 



rietes of the body by means of slender, radiated 

 filaments : its cavity is occupied by three lon- 

 gitudinal ridges, which meet in the centre and 

 reduce the canal to a triangular form. The 

 CEsophagus is separated by a well-marked con- 

 striction from the second part of the digestive 

 canal, which in the rest of its course presents 

 no natural division into stomach and intestine. 

 The anterior portion of the canal is attached 

 by filaments, as in the Strongylus, to the pro- 

 cesses and lining membrane 

 Fig. 87. of the abdominal cavity. Those 

 d which come off from the sides 



of the canal (d, d) communi- 

 cate with the nutritious vessels 

 and appendages, and in pass- 

 ing from the intestine they 

 diverge and leave on each side 

 a triangular space, of which 

 the base corresponds to the 

 lateral line or vessel (e, Jig. 

 86), and the apex to the side 

 of the intestine. These lateral 

 spaces are filled with a serous 

 fluid, and are continuous with 

 the common cavity contain- 

 ing the alimentary and gene- 

 rative tubes. About the mid- 

 dle of the body the intestine 

 becomes narrower, being here 

 surrounded and compressed 

 by the aggregated loops of the 

 oviduct or testis, and the me- 

 senteric processes or filaments 

 diminish in number, and at 

 last leave the intestine quite 

 free, which then gradually en- 

 larges to within a short dis- 

 tance of its termination (A). 



The parietes of the intestine 

 are thin and transparent, and 

 easily lacerable ; they consist 

 of a gelatinous membrane, the 

 internal surface of which is 

 disposed in irregular angular 

 meshes and transverse folds, 

 which gradually disappear to- 

 wards the lower part of the 

 canal. 



The soft obtuse processes 

 (f, ft fig. 86) analogous to 

 those which project from the 

 lining membrane of the abdo- 

 minal cavity in the Strongylus, 

 acquire a considerable deve- 

 lopment in the Ascaris. They 

 arise chiefly in the dorsal and 

 ventral regions, and are con- 

 tinued from numerous trans- 

 verse bands (e,e,jig.88} which 

 pass across the body from one 

 lateral absorbent vessel to the 

 other. In the anterior third 

 of the body these transverse 

 bands (vaisseaux nourriciers, 

 Cloquet,) are quite concealed 



Digestive and gene*? the Presses in question 

 rative tubes, Ascari*( a PP<lices nuumaers, Clo- 

 lumbricoides, male, quet), but are very conspicu- 



