The mouth (d, fig. 87 and fig. 85) is sur rounded with three tubercles, of which one is superior (a, fig. 85), the others inferior (b, to); 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 fascieulus 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 arc 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 (esophagus (e, 87) is muscular and four or five lines in length, nar row, slightly dilated pos teriorly, and attached to the muscular pa 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 (esophagus 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 Struagylas, to the pro cesses and lining membrane of theabdominal cavity. Those 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, fig. 86), and the apex to the side of the intestine. These lateral spaces are filled with a scrolls 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 (11).
The parietes of the intestine are thin and transparent, and easily laecrable ; 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 fio. 86) analogous to those which project from the lining membrane of the minal cavityin the Strimgylas, acquire a considerable lopment in the Ascaris. They arise chiefly in the dorsal and ventral regions, and are tinued from numerous trans- verse bands (e,c,fig.88) which pass across the body from one lateral absorbent vessel to the other. In the anterior third
of the body these transverse bands (vaisseau.r naiirriciers, Cloquet,) are quite concealed by the processes in question ,( appendices nourririers, quet), but are very conspicu ous at the posterior part of the body. The nervous chord passes at a right angle to the transverse bands between them and the longi tudinal muscles, and sometimes is included in loops of the former, as at d, fig. 88. Both the pendant processes and the transverse bands are composed of a homogeneous spongy tissue, without any central cavity, and appear to form a nidus of nutrient matter like the fatty omen tal processes in higher animals.
The longitudinal lines (c,c,fig. 86, 88),which extend along each side the body of the Ascaris Lumbricoides, and which are very conspicuous externally through the transparent integument, consist each of a narrow flattened tract of opaque substance, by some anatomists considered as nervous, and a very slender vessel which ad heres closely to the outer side of the band. The two bands become expanded at the an terior extremity of the body, and unite in forming a circle around the cesophagus : the vessels, on the contrary, become detached from the bands, and pass transversely below the oesophagus to anastomose together, forming a simple loop or arch, the convexity of which is anterior. 13y pressure the reddish fluid con tained in these vessels may be made to tra verse them backwards and forwards.
With respect to the accessory glands of the digestive system of the Entozoa, I have hi therto met with them in two species only of the Nentatoidca, in both of which they pre sented the primitive form of simple elongated unbranched cceca. The first being developed from the commencement of the alimentary canal, and co-existing with a pair of rudimen tal jaws, must be regarded as salivary organs. They exist in a species of worm which infests the stomach of the Tiger, and which I have recently described under the name of Gnathostoma aculeatuni.* They consist of four slender elongated cceca, communi cating with the mouth, and gradually increas ing in size as they extend backwards into the abdominal cavity, where they end each in a cul-de-sac; they are placed at equal distances around the alimentary canal, and have no at tachment except at their open anterior extre mity. The length of each ccecum is about one-twentieth of the entire alimentary canal. Their parietes under a high magnifying power present a beautiful arrangement of spirally decussating fibres. Their contents when recent are clear, but become opaque when immersed in alcohol. That the Gnathostoma is not the larva of an insect is proved by the complete development of the generative system, which resembles that of the Ascarides, and by the absence of a ganglionic nervous system.