MUTILATION AND REGENERATION 381 



becomes still more difficult if the adaptation theory be 

 entertained, for, granting that regeneration be an 

 adaptation, the failure of regeneration in those cases 

 where the new limb is substituted for the amputated 

 one never can be so regarded, seeing that the imagina- 

 tion can scarcely entertain such a thought as that of mu- 

 tilated animals finding adapted parts with which to 

 replace those lost and so doing away with the necessity 

 of preparing them. 



Though the regenerative phenomena extend through- 

 out the different phyla of animals, examples being found 

 among such vertebrates as fishes, batrachians, reptiles, 

 and birds, it does not extend to the mammals. No 

 authenticated cases are on record in which parts lost by 

 mammals have ever been regenerated. These highest 

 and most complex of living organisms are unhappy in 

 being without so useful a function. Among them 

 all that can be hoped for is that healing may follow 

 injury. 



III. The Mutilated Organism Repairs Itself Without 

 Restoring its Symmetry. This method of repair has 

 several times been referred to as "simple healing." 

 It takes place through proliferative activities of the 

 simpler epithelial and connective tissues. It also 

 includes restoration of a few damaged tissues, so as to 

 be regenerative in tendency. 



1. Epithelial Tissues. Whenever the covering epithe- 

 lium is removed by accident or destroyed by disease, 

 repair soon begins through the proliferation of cells at 

 the periphery of the denudation. The multiplying cells 

 extend more and more until, if the denuded area is not 

 so great as to occasion the death of the individual, or so 

 infected as to destroy the cells as they form, a new cover- 

 ing is produced. This new integument usually lacks the 

 appendages with which the original structure may have 

 been provided. Thus in repair of the skin, the hair 

 follicles, sweat and sebaceous glands are usually absent 

 or very few, and in the mucous membranes the glands 



