234 NATURE AND LIFE. 



produced, but much more slowly. The restoration is longer 

 in proportion as the animal is older. With crawfish under 

 a year old, all the severed limbs grow again in about sev- 

 enty days. In the case of full-grown males, their complete 

 restoration requires from eighteen months to two years, 

 and with females from three to four years. Chantran dis- 

 covered, moreover, last year, a strange phenomenon of quite 

 another kind. He proved by experiment that crawfishes' 

 eyes are reproduced after removal, and that sometimes, in 

 place of an eye taken out, two grow again. 



This is what experiment has confirmed regarding the 

 reproduction of limbs and organs in animals. We must 

 now examine in what way the tissues are restored. All 

 the tissues that have been destroyed in the full-grown sub- 

 ject the skin, nerves, muscles, bones are capable of being 

 regenerated, and they are regenerated, by going through a 

 series of phases identical with those of their embryonic de- 

 velopment, of their generation properly so called. The force 

 which has brought them to birth is the same force which 

 effects their new birth. In every case, the elements of the 

 new tissue are produced exactly like those of the old, and 

 these phenomena, in no wise unusual or exceptional, bear 

 witness once again to the unity and simplicity of physio- 

 logical mechanical action. 



The epidermis is reproduced with the greatest ease. 

 It grows again as the hair and the nails do. It is the same 

 tissue with them. The crystalline humor of the eye, which 

 may be considered like the substance of the epidermis, also 

 grows again after it has been removed. At least this is the 

 result of the very numerous experiments performed by Mil- 

 liot on dogs and rabbits. That physiologist constantly 

 observed that, after effecting with one of these animals the 

 removal of that biconvex lens which is one of the chief or- 

 gans of the system of sight, it was restored after a few 

 months. The disease known by the name of cataract con- 



