296 



REPTILIA. 



length of the intestine, and corresponds to 

 the duodenum of birds. The other part is of 

 smaller diameter, and has thicker walls, en- 

 closing between the mucous and muscular 

 tunics a layer of glandular substance, re- 

 sembling a greyish, semitransparent pulp. 

 The lining membrane of the intestine which 

 covers this glandular layer is disposed in 

 longitudinal zig-zags, connected together by 

 little folds that pass from one to another, 

 so as to constitute a fine net-work. These 

 zig-zags are replaced by delicate villosities in 

 the first portion of the small intestine, where 

 the glandular layer is not perceptible ; and 

 towards its termination in the large intestine, 

 they become reduced to undulating folds, 

 rarely joined together by transverse plicae. 

 In the larger intestine itself, they are con- 

 verted into irregular projections, which form 

 a sort of villous surface. 



In the other families of saurian reptiles, 

 the form and structure of the stomach may 

 be referred to the common type which we 

 have already seen in the Chelonians. The 

 oesophagus is wide, with very extensive walls, 

 as is indicated by the longitudinal folds of its 

 lining membrane ; it is generally of the same 

 diameter with the stomach, which latter 

 forms a cylindrical or conical bowel, directed 

 from before backwards, and generally bent 

 a little towards the right near its termination, 

 so that we may distinguish a pyloric portion 

 extending from the bend to the pylorus, the 

 length of which is very variable, and which is 

 distinguishable from the rest of the stomach 

 by the greater thickness of its coat. At the 

 entrance of the duodenum there is a promi- 

 nent muscular ring, serving the office of a 

 pyloric valve. 



The great curvature, which is generally more 

 dilated, is sometimes, though rarely, prolonged 

 into a small cul-de-sac (Monitor of the Nile}. 



The small intestine of the Laccrtidcs is short 

 and sometimes very capacious in the first half 

 of its extent ; the other half presents ligamen- 

 tous bands, which produce puckerings and 

 constrictions corresponding internally with 

 transverse ridges that intersect the oblique 

 folds of the lining membrane. This latter in 

 the large intestine forms transverse valves, 

 dividing its cavity into numerous pouches. 



The Iguanas, which live entirely upon 

 fruits, grains, and leaves, have no caecum, 

 properly so called, indicative of this regimen ; 

 but their large intestine is prodigiously de- 

 veloped, and its cavity extended by numerous 

 internal folds of the lining membrane. 



In the Ophidian reptiles, the oesophagus 

 and stomach form a continuous canal of va- 

 riable length, in which it is generally difficult 

 to say where the one terminates and the other 

 begins ; it may be remarked, however, that 

 the walls of the oesophagus are thin, and the 

 longitudinal folds of its lining membrane small 

 and few in number, whilst the commencement 

 of the stomach is indicated externallv by a 

 strengthening of the muscular fasciculi, and 

 internally by thicker and more numerous 

 longitudinal plicae of the lining tunic, which 



are often undulating, and here and there ir- 

 regular. These folds are only visible when 



Fig. 216. 



Alimentary canal of Draco viridis. 



a, tongue ; b, larynx ; c, opening leading into the 

 guttural sac; d, laiyngeal sac, e, oesophagus; /, 

 stomach ; g, g, small intestine ; h, csecal appendage 

 to the commencement of the colon ; i, colon ; ft, the 

 cloaca. 



the stomach is empty. Sometimes the cardiac 

 commencement of the stomach is indicated 

 by a kind of cul-de-sac. 



The stomach of serpents is remarkably short 

 in relation to the length of the animal and 

 the extent of the oesophagus ; its situation 

 also is very far back, so that the prey which 

 the animal swallows will be lodged partly in 

 the oesophagus and partly in the stomachal 

 cavity. The latter may be divided into two 

 portions, one of which Cuvier calls the 

 " sack " and the other the pylcvic portion. 

 The " sack " has a very different appearance 

 when empty to that which it presents when 

 distended with prey : in the first case, its 

 walls appear thick and muscular, whereas in 

 the second they are very thin and extensible. 



Before terminating in the intestine, the 

 stomach becomes considerably diminished in 

 its diameter, and is converted into a narrow 

 channel of variable length in different genera 

 and even in different species, which is but 

 little susceptible of dilation, and into which 

 the food only passes after being digested in 

 the first portion. This second division of 

 the stomach may be continuous with the 

 axis of the former; at other times it seems to 

 be given off from one side. It may be more 

 or less bent upon itself, or even form several 

 curvatures in different directions, or pass 

 straight into the intestine. When the stomach 



