Dr Barclay Smith , Extreme Visceral Dislocation. 23 



segment of the gut, it travels in opposite directions. The 

 stimulus for such contractions may be provided by the entrance 

 of the undigested material into the large gut from the small. 

 After this material has undergone sufficient digestive changes, it 

 may exert such an influence on the intestinal wall that contractions 

 of another character make their appearance, contractions whereby 

 the intestinal contents are propelled onwards and ultimately 

 evacuated. 



In birds the large intestine is remarkably short, a modification 

 which would scarcely be expected. A caecum which is in most 

 cases double is however a constant feature, and it is most marked 

 in the vegetable feeders. The reason for an abbreviated large 

 intestine is not very obvious. It is probably a modification, which, 

 together with the shortening of the whole intestinal canal met 

 with in the bird, is correlated with the development of those 

 accessory organs which are found at the proximal end of the 

 digestive tube, and play such an important mechanical part in 

 preparing the food for the action of the digestive fluids. Further, 

 even in the vegetable feeders, the food is not of such an indi- 

 gestible character as that of the typical herbivor whose diet 

 consists largely, of grasses, leaves, &c. Seeds forming the staple 

 diet of such birds, once the cellulose coat is got rid of, and the 

 substance of the seed particulated by the mechanical apparatus, 

 a material is presented with which the normal digestive fluids are 

 capable of dealing. Probably then bacterial digestion plays only 

 a subsidiary part in such cases. In some birds, however, an 

 apparatus for special bacterial digestion is a necessity owing to 

 the special character of the food. The grouse is a case in point: — 

 a yard long caecum filled with homogeneous pultaceous matter, 

 without any trace of the heather buds which are abundant in the 

 ordinary tract of the intestine, affords an extremely -suggestive 

 example 1 . 



The arrangements in the typical mammalian herbivora are too 

 well known to require notice, but it is in these animals that the 

 most extreme forms of csecal development and elongation of the 

 large gut are to be met with, and that bacteria do play an im- 

 portant and essential part in the digestive processes of the 

 herbivorous mammal is an accepted fact. 



From this brief survey it is legitimate to conclude that the 

 development of the gut on the distal side of the ileocolic valve, 

 whether in the form of a diverticulum or in the extension of 

 absorptive surface, is so universally correlated with the character 

 of the diet that they must be special adaptations for digestion and 

 absorption. 



1 Owen, Comparative Anatomy of Vertebrates, Vol. n., p. 171. 



