230 Theories Treating of Inheritance 
on, there would be a single identical influence exerted 
upon the nuclei of all the cells without exception, which 
makes it conceivable that thereby the special nuclei of the 
different cells, and consequently of the germ cells also, 
could all inherit the new reactive property, which would 
be added to the other special characters already present in 
each nucleus and different in the different cells. 
But in the case, for instance, of a certain muscle, 
which develops to a greater size because of a definite 
modification in its local, trophic, functional stimulus, is it 
possible to make the analogous statement that there is 
thus obtained a new state of the body which brings about 
a modification in the idioplasmic substance of all the cells 
of the organism without exception—the same modifica- 
tion in each of them? Certainly this modification induced 
in the trophic functional stimulus of a muscle and the 
greater development thereby provoked in it will exert an 
influence on all or nearly all parts of the organism; but 
the most probable supposition and that best corresponding 
with the facts would be that the reaction is different in 
each part. This case at least is quite different from that 
in which one has to do with the transmission of a definite 
infection or immunity, and cannot be compared with it 
without further consideration. 
In short Hertwig supposes that every local material 
modification which appears at a given point of the idio- 
plasm as a reaction to a new functional stimulus extends 
at once throughout the whole idioplasm, so that the latter 
becomes modified uniformly everywhere, like a true 
physiologic unit: 
“In the organism considered as a physiologic unit of 
life the actions of all individual organs, tissues and cells 
must be combined into a complex common action, the 
