336 BIOLOGY. [Book iv. 



Regeneration being simply, like generation, an exaggeration of 

 the property of nutrition, it is natural for it to be the prompter 

 and easier the younger the individual is. It is operated, in 

 effect, more easily in youth than in the period of maturity, 

 and more easily in the larva than in the complete animal. The 

 young salamanders reproduce their claws more easily and more 

 completely than the old. The sectionised tail of the tadpole 

 grows again the faster the younger the animal is. The perfect 

 insect does not reproduce its antennse, while this regeneration is 

 accomplished with facility in its larva ; and so on. 



The faculty of regeneration — and this is a very singular fact 

 at the very outset — seems to be almost peculiar to the animal 

 kingdom. It exists little, or not at all, in plants. A leaf or a 

 branch when cut is not remade. This fact comes in support of 

 the theory which considers every complex vegetal as an aggrega- 

 tion, a sort of colony of polypiers, of which the diverse parts have 

 their own, their individual life. Every leaf, every bud lives 

 on its own account, and the diverse parts of the vegetal are 

 connected with each other by a very feeble solidarity. 



In the superior animals and in man we do not see, as in the 

 inferior animals, an entire organ, complex, composed of diverse 

 tissues, reproduce itself in totality. But all the tissues, except 

 . perhaps the striated muscular fibre, can be reproduced isolately 

 and in small portions. 



It is a fact of vulgar notoriety and often utilised in surgical 

 therapeutics, that great quantities of osseous tissue can be 

 regenerated, and even very promptly, provided the^ vascular 

 membrane of the bone, the periosteum is uninjured. 



The regeneration of a tissue is the easier the more this tissue is 

 differentiated, the more delicate and noble are the functions to 

 which it appertaineth. Yet, in conflict with this genei-al pro- 

 position, the muscular striated tissue can be little if at all 

 regenerated, while the reproduction of the nervous tissue is not 

 rare. A sectionised or even a resectionised nerve remakes 

 itself from the injured point to its furthest ramifications, and 



