158 THE VITAL FUNCTIONS. 



by feeding a young animal at different times 

 with madder ; the teeth which are formed at 

 that period exhibiting, in consequence, alternate 

 layers of red and of white ivory.* 



The formation of the teeth of herbivorous 

 quadrupeds, which have three kinds of substance, 

 is conducted in a still more artificial and com- 

 plicated manner. Thus in the Elephant, the 

 pulp which deposits the ivory is extended in the 

 form of a number of parallel plates ; while the 

 capsule which invests it, accompanies it in all 

 its parts, sending down duplicatures of mem- 

 brane in the intervals between the plates. 

 Hence the ivory constructed by the pulp, and 

 the enamel deposited over it, are variously inter- 

 mixed ; but besides this, the crusta petrosa is 

 deposited on the outside of the enamel. Cuvier 

 asserts that this deposition is made by the same 

 capsule which has formed the enamel, and which, 

 previously to this change of function, has become 

 more spongy and vascular than before. But 

 his brother, M. Frederic Cuvier represents the 

 deposit of crusta petrosa, as performed by a third 

 membrane, wholly distinct from the two others, 

 and exterior to them all, although it follows them 

 in all their folds. In the Horse and the Ox, the 

 projecting processes of the pulp, have more of a 

 conical form, with undulating sides ; and hence 



* Cuvier. Dictionnaire des Sciences Medicales, t. viii. p. 320. 



