224 THE VITAL FUNCTIONS. 



contrast is still more strongly marked in birds. 

 The Cassowary of Java, which lives amidst a 

 most luxuriant supply of food, has a colon of one 

 foot in length, and two caeca, each of which is 

 six inches long, and one quarter of an inch in 

 diameter. The African ostrich, on the other 

 hand, which inhabits a country where the supply 

 of food is very scanty, has a colon forty-five 

 feet long ; each of the caeca is two feet nine 

 inches in length, and, at the widest part, three 

 inches in diameter ; in addition to which there 

 are broad valves in the interior of both these 

 cavities.* 



On comparing the structure of the digestive 

 organs of Man with those of other animals 

 belonging to the class Mammalia, we find them 

 holding a place in the series intermediate be- 

 tween those of the purely carnivorous, and ex- 

 clusively herbivorous tribes ; and in some mea- 

 sure uniting the characters of both. The powers 

 of the human stomach do not, indeed, extend to 

 the digestion either of the tough woody fibres of 

 vegetables on the one hand, or the compact 

 texture of bones on the other ; but still they are 

 competent to extract nourishment from a wider 



* Lectures, &c. I. 470. In the account above given of the 

 digestive organs I have purposely omitted all mention of the 

 spleen; because, although this organ is probably in some way 

 related to digestion, the exact nature of its functions has not yet 

 been determined with any certainty. 



