190 



OEGAJ^S OF DIGESTION. 



tusks, or carnivorous teeth, canines ; and the grinders, molars 



(fig. 205). The 

 incisors occupy 

 the front of the 

 mouth ; they are 

 the most simple 

 and the least va- 

 ~ ried ; they have 

 a thin cutting 

 summit, and are 

 employed almost 

 Fig. 205. The skull of a horse. exclusively for 



seizing food, except in the elephant, in which they assume the 

 form of large tusks. The canines are conical, more prominent 

 than the others, more or less curved, and only two in each jaw; 

 they have but a single root, like the incisors, and in the carni- 

 vora become very formidable weapons. In the herbivora they 

 are wanting, or, when existing, they are usually so enlarged 

 and modified as also to become powerful organs of offence and 

 defence, although useless for mastication, as in the babyroussa. 

 The molars are the most impor- 

 tant for indicating the habits and 

 internal structure of the animal, they 

 are, at the same time, most varied in 

 shape. Among them we find every 

 transition, from those of a sharp and 

 pointed form, as in the cat tribe (fig. 

 207), to those with broad and level 

 summits, as in the ruminants and 

 rodents (fig. 206) ; still, when most diversified in the same 

 animal, they have one character in common, their roots being 

 never simple, but double or triple, a peculiarity which not only 

 fixes them more firmly, but prevents them from being driven 

 into the jaw in the efforts of mastication. 



342. The harmony of organs, already spoken of, is illus- 

 trated, in the most striking manner, by the study of the teeth 

 of mammals, and especially of their molar teeth. So constantly 

 do they correspond with the structure of other parts of the 

 body, that a single molar is sufficient not only to indicate the 

 mode of life of the animal to which it belongs, and to show 

 whether it fed on flesh or vegetables, or both, but also to de- 



Fig. 206. The skull of a 

 squirrel. 



