ANIMAL GRAFTS AND REGENERATIONS. 235 



sists in the loss of its transparency by the crystalline humor, 

 and in its becoming opaque, so that the rays of light no 

 longer pass through it. The only remedy for this disorder 

 in the eye is the operation called that for cataract, which 

 consists in removing the crystalline lens. The eye thus 

 operated on does not regain its original clearness of sight, 

 but it can perceive light and outward objects much better 

 than with its crystalline lens impenetrable to rays of light. 

 The crystalline humor removed in such a case from the hu- 

 man subject is not renovated ; but, by pursuing investiga- 

 tions of the kind which Milliot has begun, we may hope to 

 discover the conditions of such a reproduction, which would 

 be priceless to surgery. Restoration of the skin is noticed 

 in all ordinary scars. The tissue of scars is made up of 

 the usual anatomical elements composing the derma, that 

 is, chiefiy of laminated or elastic fibres. The vessels that 

 are torn or broken, the severed tendons, in like manner, re- 

 pair with the greatest ease those losses of substance they 

 have suffered. In a word, in all these organs there is a 

 tendency, observed by surgeons of every age, toward re- 

 generation, a plastic and radiant force which makes itself 

 known by an unceasing elaboration of blastema, within 

 which new anatomical elements grow forth to supply the 

 void of those removed. 



Regeneration of nerves was remarked for the first time 

 by Michaelis, Cruikshank, Monro, and Haighton, in the lat- 

 ter part of the last century. In 1801, Bichat expressed a 

 perfect theory of it, with admirable clearness. Upon in- 

 terruption of the continuity of a nerve, the severed part 

 can reproduce itself after a certain time. When, for in- 

 stance, a segment a centimetre long is cut out from the 

 sciatic nerve, there is at first remarked a change in the 

 nerve-substance of the ends produced by cutting ; then, six 

 weeks or two months after the operation, we see a grayish 

 bunch proceeding from the point of one of the ends, 



