Roux's Self Regulating Mechanism 95 
primitive state. Thus it is that a wound or a fracture 
is never so detrimental to the child as to the adult; but 
it is also true that with the same intensity and duration 
of the educative influence directed toward the modifica- 
tion of inborn tendencies the results are more permanent 
the older the child is. 
This elasticity of development is proved by Roux 
with his customary care in the following way. 
In one of his experiments on the effects of passive 
deformations in the first stages of development he suc- 
ceeded in bending a few frogs’ embryos within their 
gelatin envelopes by squeezing them between needles. “If 
the needles were removed immediately after the deforma- 
tion, the embryo at once took on again its previous form; 
if they remained however a few hours the deformation 
tended to be a persistent one and disappeared again 
only in the course of several hours; a proof that an inter- 
nal adaptation to the new form had already commenced, 
but which was in its turn caused to disappear in the 
course of further development, perhaps by the action of 
growth forces inhibited during the deformation but re- 
sumed upon the restoration of the normal form.” ° 
Roux gives this dynamic elasticity of development 
the name “mechanism of self regulation.” Let us note 
again that the absence of this elasticity in adult organisms, 
which remain plastic in relation to the somewhat persist- 
ent, deforming influences of the environment, would de- 
note that this mechanism is active only during embryonic 
life. Now the continued action exercised by the central 
zone of development constitutes precisely such a mechan- 
*Wilhelm Roux: Zur Orientierung tiber einige Probleme der 
embryonalen Entwicklung. Zeitschr. f. Biol. Bd. XXI. Miinchen, 
July 1885. P. 515—516. Gesamm. Abhandl. Zw. Bd. P. 24s. 
