296 



REPTILIA. 



length of the intestine, and corresponds to are often undulating, and here and there ir- 

 the duodenum of birds. The other part is of regular. These folds are only visible when 



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 



Fig. 216. 



Alimentary canal of Draco viridis. 

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

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



by the greater thickness of its coat. At the stomach; g, & small intestine; h, csecal appendage 



entranc! of the duodenum there is a promi- to^he commencement of the colon; ,, colon; k, the 

 nent muscular ring, serving the office of a 



pyloric valve. the stomach is empty. Sometimes the cardiac 



The great curvature, which is generally more commencement of the stomach is indicated 



dilated, is sometimes, though rarely, prolonged by a kind of cul-de-sac, 



into a small cul-de-sac (Monitor of the Nile}. The stomach of serpents is remarkably short 



The small intestine of the Lacertidce is short in relation to the length of the animal and 



and sometimes very capacious in the first half the extent of the oesophagus ; its situation 



of its extent; the other half presents ligamen- also is very far back, so that the prey which 



tons bands, which produce puckerings and the animal swallows will be lodged partly in 



constrictions corresponding internally with the oesophagus and partly in the stomachal 



transverse ridges that intersect the oblique cavity. The latter may be divided into two 



folds of the lining membrane. This latter in 

 the large intestine forms transverse valves, 

 dividing its cavity into numerous pouches. 



portions, one of which Cuvier calls the 

 "sack" and the other the pyloric portion. 

 The " sack " has a very different appearance 



The IguanaSy which live entirely upon when empty to that which it presents when 



fruits, grains, and leaves, have no caecum, distended with prey : in the first case, its 



properly so called, indicative of this regimen ; walls appear thick and muscular, whereas in 



but their large intestine is prodigiously de- the second they are very thin and extensible, 

 veloped, and its cavity extended by numerous Before terminating in the intestine, the 



internal folds of the lining membrane, 



stomach becomes considerably diminished in 



In the Ophidian reptiles, the oesophagus its diameter, and is converted into a narrow 



and stomach form a continuous canal of va- channel of variable length in different genera 



riable length, in which it is generally difficult and even in different species, which is but 



to say where the one terminates and the other little susceptible of dilation, and into which 



begins ; it may be remarked, however, that the food only passes after being digested in 



the walls of the oesophagus are thin, and the the first portion. This second division of 



longitudinal folds of its lining membrane small the stomach may be continuous with the 



ajid few in number, whilst the commencement axis of the former; at other times it seems to 



of the stomach is indicated externally by a be given off from one side. It may be more 



strengthening of the muscular fasciculi, and or less bent upon itself, or even form several 



internally by thicker and more numerous curvatures in different directions, or pass 



longitudinal plicas of the lining tunic, which straight into the intestine. When the stomach 



