ANIMALS AND THEIR DIET. 407 



ous type as witnessed in the tiger or the polecat. Yet such species, as we may 

 infer from the very fact of their existence, are not thereby injured. 



We know that the greatest mass of vegetables, especially the leaves, stalks, 

 and even the roots and the fleshy pa.rt of the fruits, are less nutritious than is or- 

 dinary animal matter. To this rule the seeds of a number of plants, such as the 

 legumens and the various kinds of grain, form an exception, though even here it 

 would appear that a part of the nitrogenous matter is not present in a state suita- 

 ble for assimilation. In other words, it exists not entirely in an albuminoid but 

 in an amidic state. Hence we must conclude that an animal which is to exist 

 entirely upon a vegetable diet must have larger digestive organs, so as to operate 

 upon the greatest quantity of matter at once. On the other hand, purely zoo- 

 phagous species require, or at least can exist with, a smaller and simpler digestive 

 apparatus. We may go a step further : of all nutriment the poorest — /'. e., that 

 which contains the smallest quantity of blood-forming matter — consists of leaves 

 and stalks. Accordingly the Ruminants, which feed upon leaves and stalks, 

 have the largest and most complicated stomachs. In the Solidungula, of which 

 the horse and ass are typical specimens, the diet is the same as that of the Rum- 

 inants, but the stomach is simple, and digestion is in consequence far less per- 

 fectly performed, as an inspection of the respective excrements of the horse and 

 the ox will readily show. May it not be that we have here the reason why the 

 Solidungula as a sub-order are so far less rich in forms and less widely distribut- 

 ed? We come now to such animals as the swine. Here the divisions of the 

 stomach occurring in the Rumimants are but faintly marked out, to suit a richer 

 diet, composed largely of roots mixed with no inconsiderable proportion of ani- 

 mal matter. A step further we find the apes feeding on fruits and nuts, with the 

 addition of eggs, larvae, etc. Here the stomach is simple, and the whole diges- 

 tive apparatus lighter in proportion to the entire body than that of the swine. 

 Lastly, in the true Carnivora, where the diet is most concentrated, we find the 

 digestive canal shortest, and the relative weight of the stomach and its append- 

 ages smallest. 



Another point of difference between animal and vegetable matters is that 

 the former require less preparation before they can be assimilated. Hence we 

 find that the teeth of the dog or cat, besides their action in seizing and killing 

 the prey, need merely to tear it into lumps of a convenient size for swallowing. 

 When this is once done digestion is not difficult. Vegetable food, on the other 

 hand, requires to be ground to a pulp, so that the saliva and the gastric and pan- 

 creatic secretions may act upon its smallest particles. Hence true molar teeth 

 are required, destined not to cut, but to pulverize. We see an approach to this 

 structure even in the bears. But for the poorest kinds of vegetable food this ar- 

 rangement is not sufficient; the leaves and stalks eaten, consisting as they do 

 largely of cellulose, — which man cannot digest at all, — have to go through that 

 double preparation commonly known as chewing the cud. 



We may now venture to assign a reason why it is easier for a phytophagous 

 animal/ to turn zoophagous, than for a zoophagous creature to become phytopha- 



