358 FISHES. 



squalus, extend even their continuity as far as the pericardium, and 

 along all its internal lamina*. 



The intestinal canal is composed of the same tunics as in other ver- 

 teb rated animals, and the variations which they undergo in their respec- 

 tive thicknesses and their different folds, are analogous to Avhat is 

 seen in the higher classes, and are not less numerous : it has valvulae 

 conniventes and internal papilla? of different forms, also coriaceous 

 indurations and wrinkles in various directions. The fleshy fibres are 

 reinforced or they become weak ; sometimes a glandular tissue is 

 placed between the membranes, &c. 



The internal folds of the oesophagus are usually longitudinal : its 

 cavity is continued in a right line to the bottom of the cul-de sac of 

 the stomach ; sometimes even, as in the cyprins, and labrus, the stomach 

 has no cul-de sac, and is merely a slight dilatation of the canal which 

 scarcely deserves the name of stomach ; but, very often, it is curved, 

 or it is directed from a part more or less adjacent to the entrance, 

 and from the right side a branch at the extremity of which is the 

 pylorus. This branch, which is transverse and even ascending, as- 

 sumes, sometimes, as in the grayling and the mullet, such a thickness 

 in its fleshy tunic that it constitutes a true gizzard, of which the ordi- 

 nary stomach represents in such a case, the crop. 



The size of the sac forming the stomach, the proportions of its 

 length and breadth, the thickness of its walls, its wrinkles, &c, are 

 infinitely varied, and the description of them could only properly find 

 a place in the individual histories of the species. 



The intestinal canal is more or less long, more or less broad, and 

 forms also more or less folds : its walls vary in thickness, villosities 

 are more or less marked according to the species. Thus one fish, as 

 the lamprey, has all straight, others as many of the percoides,form only 

 two or three folds, and the third, as the hypostome has it as thin as a 

 cord, and sufficiently long to exceed many times the length of its 

 body. But these are details for individual histories to enter upon. 



There is generally on the side of the anus a small valve, separating 

 the posterior from the anterior part ; but, in very rare instances only, 

 is this posterior portion beyond the size of the other, and, in no in- 

 stance, has it a coecum as is found in the quadrupeds. 



One of the most remarkable folds that has hitherto been observed 

 in the intestines of fishes, is the little spiral valve of the rays, of 

 squalus, and the sturgeon ; and of this valve vestiges are found even 

 in the lamprey. 



Close to the pylorus in a great number of fishes Avill be found blind 

 guts, and these often in a considerable number, and of Avhich the 

 velvetty surface, folded into dense meshes, would appear to furnish in 

 a great abundance a glary liquid, which is regarded as having a re- 

 semblance to the pancreatic juice, and which is so much the more 

 beneficial, since fishes, as we have already mentioned, are generally 

 without salivary glandsf . 



* Munro, Anatomy of Fishes, pi. 1. fig. 5, No. 28, shows the openings of the 

 abdomen, and plate 2, fig. l , Nos. 22, 23, those of the pericardium in the rays ; 

 pi. 8 shows those of the abdomen of the sturgeon. 



f M. Rathke is of opinion that the spungy substance in the palate of the carp and 



