184 GIGANTIC TERRESTRIAL SAURIANS. 



form like thai of the two-edged point of a sabre, cutting 

 equally on each side. As the tooth advanced in growth, it 

 became curved backwards, in the form of a pruning knife, 

 (PI. 23, Figs. 1. 2. 3.) and the edge of serrated enamel was 

 continued downwards to the base of the inner and cutting 

 side of the tooth, (Fig. 1 , B. D.) whilst, on the outer side, 

 a similar edge descended, but to a short distance from the 

 point (Fig. 1, B. to C.) and the convex portion of the tooth 

 (A.) became blunt and thick, as the back of a knife is made 

 thick, for the purpose of producing strength. The strength 

 of the tooth was farther increased by the expansion of its 

 sides, (as represented in the transverse section, Fig. 4, A. D.) 

 Had the serrature continued along the whole of the blunt 

 and convex portion of the tooth, it would, in this position, 

 have possessed no useful cutting power ; it ceased precisely 

 at the point, (C.) beyond which it could no longer be effective 

 In a tooth thus formed for cutting along its concave edge, 

 eacii movement of the jaw combined the power of the knife 

 and saw ; whilst the apex, in making the first incision, acted 

 like the two-edged point of a sabre. The backward cur- 

 vature of the full-grown teeth, enabled them to retain, like 

 barbs, the prey which they had penetrated. In these 

 adaptations, we see contrivances, which human ingenuity 

 has also adopted, in the preparation of various instruments 

 of art. 



In a former chapter (Ch. XIII.) I endeavoured to show 

 that the establishment of carnivorous races throughout the 

 animal kingdom tends materially to diminish the aggregate 

 amount of animal suffering. The provision of teeth and 

 jaws, adapted to effect the work of death most speedily, is 

 highly subsidiary to the accomplishment of this desirable 

 end. We act ourselves on this conviction, under the im- 

 pulse of pure humanity, when we provide the most efficient 

 instruments to produce the instantaneous, and most easy 

 death, of the innumerable animals that are daily slaughtered 

 for the supply of human food. 



