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, chiefly 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, 
