Conceptions of Vital Energy Reviewed 333 
We have already seen also that Claude Bernard, in 
agreement with that, considers the sensibility of the ner- 
vous substance as nothing else than a particular modality 
of irritability, which would be a general property of 
all living substance. ‘‘Sensibility,” writes he, ‘considered 
as a property of the nervous system, is only a higher 
degree of a simpler property which exists everywhere 
in all living substance both animal and vegetable. It 
has nothing essential or specifically distinct. It is the 
special irritability of the nerve just as the property of 
contraction is the special irritability of the muscle, and 
as the property of secretion is the special irritability of 
the glandular element. These phenomena are so many 
different degrees of one and the same elementary phe- 
nomenon.” 254 
Bard also remarks that if the nature of the energy 
constituting the basis of all vital phenomena must be 
single, the infinitely varied modalities which the same 
vital phenomena present must then be due to as many 
corresponding modalities of this single energy. 
“In spite of the complexity and multiplicity of physio- 
logical functions,” he writes, “it is possible to refer them 
fundamentally to a general function of the living cell, 
namely the function of producing derived substances. 
Cellular specificity can be explained and made compre- 
hensible only as this single function is able to insure the 
innumerable functions necessary for an entire organism. 
The variety of derived substances is itself the effect and 
the proof of the radically different vital properties of 
the kinds of cells which create each of them.” 
“It is necessary to establish an essential difference 
231Claude Bernard: Lecons sur les phénoménes de la vie com- 
muns aux animaux et aux végétaux. P. 289—z290. 
