304 



STOMACH AND INTESTINE. 



The insectivorous Marsupials have a longer 

 intestinal canal, which is separated into large 

 and small intestine, and exhibits a caecum of 

 moderate size. Those that live upon fruits 

 have bowels which are still longer, and a 

 large caecum of twice the length of the whole 

 bod) r . Finally, the true vegetivorous genera 

 have a caecum which is thrice as long as the 

 body. In those which are possessed of a saccu- 

 lated stomach, the caecum is, however, much 

 shorter. One genus, the Wombat, has a 

 vermiform appendix. The length of the whole 

 intestine varies from two to ten times the 

 length of the animal. 



In the Moitotremafa the alimentary canal is 

 chiefly remarkable from its terminating in a 

 cloaca common to it and the urinary and 

 generative organs. A small caecum separates 

 the long and narrow bowel into two parts. 

 The diameter of the small intestine gradually 

 diminishes to the caecum, while that of the 

 large intestine gradually increases to the rec- 

 tum. 



The Cctacea offer two chief varieties of 

 stomach, which are connected with differences 

 in their food, though scarcely explained by 

 them. Those which live on vegetable food 

 exhibit a simpler form of organ. Thus, in the 

 Dugong, the stomach is long and transverse ; 

 and is divided by a deep constriction into a 

 globular cardiac, and a conical pyloric, portion. 

 Two large ca?ca open into it near this con- 

 striction ; and a special glandular apparatus 

 occupies the upper part of the cardiac pouch. 

 In the carnivorous Cetaceans, the stomach is 

 subdivided into three, five, seven, or more cavi- 

 ties. In some genera, however, there are only 

 four. Of these the first has an epidermoid 

 lining, while the three last have a soft mucous 

 membrane. The biliary duct often opens into a 

 dilated cavity, the import of which is unknown. 

 The intestine is longer in the herbivorous di- 

 vision. Here there is also a caecum ; which 

 is sometimes large and glandular, but some- 

 times small, short, and even bifid. In the 

 zoophagous Cetaceans there is rarely either 

 caecum or valve: so that the intestine, which 

 decreases slightly in size from the pylorus to 

 the anus, offers no separation into large and 

 small. But in the genus Balccnu there is a 

 small caecum, like that of the Cat. 



The Quadrumana possess a stomach the 

 form of which approaches that of the human 

 organ. In some cases, however, it is more 

 elongated ; while in others it assumes a glo- 

 bular shape, with a cardiu and pylorus in close 

 proximity. The latter deviation is generally 

 found in conjunction with carnivorous or 

 insectivorous habits. It is usually separated 

 into two portions, a cardiac and a pyloric ; and 

 sometimes the latter, which is more globul ,ir 

 than usual, is distinguished by an internal 

 fold from a short tubular part, which termi- 

 nates in the pyloric valve and the duodenum. 

 Rudimentary pyloric caeca have been remarked 

 by Cuvier * in one instance. The Sent* 

 nopllhccus presents a form of stomach which 



* Le9ons d'Anat. Comp. vol. iv. p. 28. 



recalls that of the Kangaroo. For the cardiac 

 cavity, smooth and almost bifid at its com- 

 mencement, is soon sacculated by a superior and 

 inferior band of longitudinal fibres which come 

 from the oesophagus ; and from thence the sto- 

 mach continues to the right side, as a saccu- 

 lated tube, which is bent upon itself, and closely 

 resembles a large intestine. But before reach- 

 ing the pylorus, these sacculi diminish and dis- 

 appear. 



The length of the intestinal canal in the 

 different genera of this order varies to an 

 extent which is curiously contrasted with the 

 general similarity of their food. Its proportion 

 to the length of the body is in some as 8 to 1 ; 

 in others as 3 to 1 only. The division into 

 two portions, and the general arrangement of 

 both small and large intestine, is very similar to 

 that seen in man. In all the genera a caecum 

 exists, but with great variety as to length : an 

 increased development of this portion of intes- 

 tine, as well as of the cardiac extremity of the 

 stomach, being sometimes connected with a 

 diminution in the length of the whole canal. 

 The Apes and Gibbons possess a vermiform 

 appendix ; but in the latter it is of very small 

 size. The mucous membrane has villi, but no 

 valvulae conniventes. 



General remarks. Although physiology at 

 present scarcely pretends to interpret this 

 various and complex development of the ali- 

 mentary canal, still some attempt at its expla- 

 nation is indispensable. For without any clue 

 to their import, details like the preceding 

 could hardly be recollected, far less made 

 use of; and would scarcely deserve to be 

 stored up in the archives of science, much more 

 brought forward in an essay like this. Nor, in 

 attempting their explanation, can one be rightly 

 charged with breaking those rules which o in- 

 great countryman has laid down for the pursuit 

 of natural knowledge. All that is necessary to 

 such a superstructure of theory is, that, how- 

 ever slight and temporary, it should at least be 

 founded on the known facts ; that it should in- 

 dicate something like the degree of probability 

 assignable to its several parts; and, finally, that 

 it .should be at once yielded up, as soon as a 

 stricter logic, or larger and more numerous 

 facts, offer us a better explanation. 



The absence of all digestive cavity is the first 

 peculiarity which demands our notice. The 

 few genera in whom this rare condition has 

 been found all offer the greatest simplicity of 

 structure; and further agree in the fact that 

 they are parasitic : L e. that they derive their 

 nutriment from the juices of another animal, 

 to whose body they are attached. Hence we 

 need not scruple to assign this apparent defi- 

 ciency of the digestive organ, partly to the pre- 

 vious elaboration of a highly nutritious animal 

 food, partly to the simplicity of the various 

 tissues which are destined to be nouiished by 

 it. But can we therefore say, that the function 

 of digebtion is absent, or what would be 

 nearly equivalent to such an assertion that 

 it is reduced to a mere physical absorption ? 

 Probably not. For, as regards the general de- 

 velopment of the animal series, comparative 



