PLANT-EATING MAMMALS 167 



and their digestive organs are of corresponding size. One result 

 of this is that the abdomen is large as compared with the thorax, 

 the proportions being reversed in carnivorous forms, which have 

 to deal with a comparatively small bulk of highly nutritious matter. 

 The Horse is not an extreme case, for it feeds little and often, as 

 compared with some other forms living on the same kind of food, 

 but the general proportions of its body are strikingly different 

 from those of a dog or cat, for the reason indicated among 

 others. Once swallowed, a large digestive and absorptive sur- 

 face is necessary to deal successfully with vegetable food, and to 

 meet this requirement the food -tube of herbivores is both long 

 and more or less possessed of swollen regions. We have seen, 

 for example, that the stomach of the leaf-eating Entellus Monkey 

 is large and divided into several compartments. As to length, 

 the Horse affords a good illustration of the principle, for its 

 intestines are from ten to twelve times the length of the body, 

 while in a cat they are only four or five times as long. The 

 stomach of a horse is not specially capacious and its shape is 

 simple, but an interesting feature may be noted in the character 

 of its lining, which in the left-hand part is hard and tough, while 

 in the right-hand portion it is soft and glandular, secreting the 

 important digestive fluid known as gastric juice. In other words, 

 the right-half region is that which is especially concerned with 

 chemical digestion. The digestive tube of the Horse does, how- 

 ever, possess an exceedingly large dilated region in the blind 

 pouch or cacum, which grows out from the beginning of the 

 large intestine. It is probable that this has to do with the 

 digestion of plant -membranes, which are composed of cellulose ', 

 a substance which, though allied to starch and sugar in com- 

 position, is notoriously difficult to digest, as human beings often 

 find to their cost if they swallow the skins of grapes, gooseberries, 

 and other fruits. 



Turning now to the Ox (Bos taurus), we find that, as in the 

 horse, there is a strongly -developed elastic neck -ligament (the 

 pax-wax of butchers), having the use already mentioned. The 

 mouth is placed on a large blunt muzzle, and the lips are com- 

 paratively immobile, their food being grasped in this case by 

 the large rough tongue, which is extremely flexible, and can 

 seize tufts of herbage, drawing them into the mouth. The teeth 

 present features which are characteristic of most common rumin- 



