166 THE FOOD OF ANIMALS 



Flower remarks (in The Horse: A Study in Natural History) : 

 " Anyone who has seen a horse take a small piece of sugar from 

 a child's hand will appreciate the delicacy and efficiency of these 

 organs as instruments of prehension". Perissodactyles generally 

 are distinguished by lips of this kind, and in the Tapirs (see 

 vol. i, p. 105) the snout is produced into a short mobile proboscis, 

 partly formed by extension of the upper lip. The nature of the 

 food is commonly indicated by the characters of the teeth, and 



Fig. 417. Complicated Grinding-teeth of Horse (Equus caballus] 



this is strikingly exemplified in the Horse (fig. 417). Incisors 

 for cutting through grass and the like are well developed in both 

 jaws, but canines, not being required, as in the Carnivora, for 

 seizing prey, are not well developed, and in the Mare are either 

 entirely absent or represented by mere vestiges. Adaptation to 

 vegetable food comes out strongly in the complex cheek-teeth, 

 which possess long grinding crowns, marked by a complicated 

 series of folds and ridges. And it is particularly noticeable that 

 the projecting part or crown of a horse's tooth not only con- 

 sists of hard dentine and very hard enamel, as in a human molar, 

 but also of a great deal of a bony substance, cement, which fills 

 up the " valleys" in the crown, instead of, as in simpler cases, 

 being confined to a thin layer on the parts imbedded in the gum. 

 In this way unequal wear is provided for by which the top of 

 the crown is always kept rough, instead of wearing down to a 

 smooth ineffective surface, as would otherwise be the case. The 

 teeth of a tapir or rhinoceros are much less complicated than 

 this, but a study of the genealogy of the Horse, as established by 

 fossils, shows that in the course of ages comparatively short and 

 simple cheek-teeth, not unlike those of tapirs, have gradually 

 attained the specialized condition which is now so characteristic. 

 Herbivorous animals, in order to obtain the nutriment which 

 they require, have to take in a comparatively large bulk of food, 



