CHAPTER V 

 REGENERATION AND LIABILITY TO INJURY 



THERE is a widespread belief amongst zoologists that a definite 

 relation exists between the liability of an animal to injury and its 

 power of regeneration. It is also supposed that those individual 

 parts of an animal that are more exposed to accidental injury, or to 

 the attacks of enemies, are the parts in which regeneration is best 

 developed, and conversely, that those parts of the body that are rarely 

 or never injured do not possess the power of regeneration. 



Not only do we find this belief implied in many ways, but we find 

 this point of view definitely taken by several eminent writers, and in 

 some cases carried so far that the process of regeneration itself is sup- 

 posed to be accounted for by the liability of the parts to injury. In 

 order that it may not appear that I have exaggerated the widespread 

 occurrence of this belief, a few examples may be cited. 



Reaumur in 1742 pointed out that regeneration is especially char- 

 acteristic of those animals whose body is liable to be broken, or, as in 

 the earthworm, subject to the attacks of enemies. Bonnet (1745) 

 thought that such a connection exists as has just been stated, and 

 that the animals that possess the power of regeneration have been 

 endowed with germs set aside for this very purpose. He further 

 believed that there would be in each animal that regenerates as many 

 of these germs as the number of times that it is liable to be injured 

 during its natural life. Darwin in his book on Animals and Plants 

 under Domestication says : " In the case of those animals that may 

 be bisected, or chopped into pieces, and of which every fragment will 

 reproduce the whole, the power of regrowth must be diffused through- 

 out the whole body. Nevertheless, there seems to be much truth in 

 the view maintained by Professor Lessona 1 that this capacity is gen- 

 erally a localized and special one serving to replace parts which are 

 eminently liable to be lost in each particular animal. The most strik- 



1 Delage and Giard give Lessona ('69) the credit for first stating that the phenomenon 

 of regeneration is an adaptation to liability to injury; but Reaumur first suggested this idea 

 in 1742, and Bonnet in 1745. Delage's interpretation, viz. that Lessona ascribed this to 

 a prevoyance de la nature, has been denied by Lessona's biographer, Camerano (La Vita 

 di M. Lessona, Acad. A', d. Torino, 2, XLV, 1896), and by Giard (Sur L'aulotomie Para- 

 sitaire, etc., Compt. Rendus de Seances de la Societe de Biologie, May, 1897). 



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