ae 
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 sey- 
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- 
velopmeut, 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. Itis thesame 
tissue with them. The crystalline humor of the eye, which 
may be considered like the substance of the epidermis, also 
grows again after ithas 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 Jens 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- 
