Functional and Ontogenetic Stimuli Alike 305 
essence to functional life proper.” 22? This would speak 
for the gradual accomplishment of the transition from 
the embryonal to the functional period without any sud- 
den and precipitate change, and so speaks also for a 
gradual, hardly noticeable replacement of the ontogenetic 
stimulus by the functional so that one must suppose the 
two stimuli to be active simultaneously ‘and in 
combination. 
So Hyrtle, having cut across the motor nerves of the 
muscles of one side of the face of a new born rabbit, 
stated that a year after there was not only atrophy of 
the muscles but the bones of that side of the head had 
undergone a surprising arrest of growth. He attributed 
this arrest to the fact that ‘after muscular paralysis there 
was lacking the traction and compression, which provoke 
living parts of the bone to activity and cause the normal 
growth of the bone.” 22% 
Alesandrini and E. H. Weber similarly found in 
monsters “that in the absence of the anlage of the spinal 
cord there were lacking in the corresponding nerve ter- 
ritory both the nerves and the muscles and that the bones 
and joints belonging to these were abnormally formed, 
the latter being in part rigid.” °?* 
It may be remarked here that as some of these parts 
had attained a certain development even without the 
functional stimulus, and during the very period in which 
normally they would have had the co-operation of the 
functional stimulus, it is therefore clear that if there had 
22Roux: Zur Orientierung iiber einige Probleme der embry- 
onalen Entwicklung. Zeitschrift fiir Biologie. Bd. XXI; Munchen, 
July 1885, P. 503. Gesammelte Abhandlungen, II, P. 231—232. 
222Qscar Hertwig: Die Zelle und die Gewebe. II, P. 175. 
224Roux: Der Kampf der Teile im Organismus. P. 51. 
