HOW ANIMALS EAT 2/1 



chisel-shaped front teeth are fitted for cutting the food, 

 and hence called incisors. These vary in number : the 

 lion has six in each jaw ; the squirrel has two in each 

 jaw, but remarkably developed ; the ox has none in the 

 upper jaw, and the elephant none in the lower ; while 

 the sloth has none at all. 80 The canines, so called 

 because so prominent in the dog, are conical, and, 

 except in man, longer than the other teeth. They are 

 designed for seizing and tearing ; and they are the most 

 formidable weapons of the wild carnivores. There are 

 never more than four. They are wanting in all rodents, 

 and in nearly all herbivorous quadrupeds. The molars, 

 or grinders, vary greatly in shape, but closely correspond 

 with the structure and habits of the animal, so that a 

 single tooth is sufficient to indicate the mode of life 

 and sometimes to identify the species. 81 In the rumi- 

 nants, rodents, horses, and elephants, the summits of 

 the molars are flat, like millstones, with transverse or 

 curving ridges of enamel. In the cats and dogs, they 

 are narrow and sharp, passing by each other like the 

 blades of scissors, and therefore cutting, rather than 

 grinding, the food. The more purely carnivorous the 

 species, and the more it feeds upon living prey, the fewer 

 the molars. In animals living on mixed diet, as the hog 

 and man, the crowns have blunt tubercles. Premolars, 

 or bicuspids, are those which were preceded by milk 

 teeth ; the true, or back, molars had no predecessors. 



The dentition of mammals is expressed by a formula, 

 which is a combination of initial letters and figures in 

 fractional form, to show the number and kind of teeth 

 on each side of both jaws. Thus, the formula for man 



The teeth of mammals are always restricted to the 

 margins of the jaws, and form a single row in each. 



