288 LIFE AND DEATH. 



similar aptitude for repairing their mutilations. 

 Pasteur, in an early work, discussed these curious 

 facts. Other experimenters, Gernez a little later and 

 Rauber more recently, took up the same subject, but 

 could do no more than extend and confirm his 

 observations. Crystals are formed from a primitive 

 nucleus, as the animal is formed from an egg ; their 

 integral particles are disposed according to efficient 

 geometrical laws, so as to produce the typical form 

 by a constructive process that may be compared to 

 the embryogenic process which builds up the body of 

 an animal. Now this operation may be disturbed by 

 accidents in the surrounding medium or by the 

 deliberate intervention of the experimenter. The 

 crystal is then mutilated. Pasteur saw that these 

 mutilations repaired themselves. " When," said he, 

 " a crystal from which a piece has been broken off is 

 replaced in the mother liquor, we see that while it 

 increases in every direction by a deposit of crystalline 

 particles, activity occurs at the place where it was 

 broken off or deformed ; and in a few hours this 

 suffices not only to build up the regular amount 

 required for the increase of all parts of the crystal, 

 but to re-establish regularity of form in the mutilated 

 part." In other words, the work of formation of the 

 crystal is carried on much more actively at the point 

 of lesion than it would have been had there been no 

 lesion. The same thing would have occurred with a 

 living being. 



Mechanism of Reparation. — Gernez some years later 

 made known the mechanism of this reparation, or, at 

 least, its immediate cause. He showed that on the 

 injured surface the crystal becomes less soluble than 

 on the other facets. This is not, however, an ex- 



