NUTRITION. 
vegetable structure to exercise these varied 
attractions, our knowledge is at present very 
limited. It will probably long remain an ulti- 
mate fact in physiology that cells have the 
power of growing from germs, of undergoing 
certain transformations, and of producing germs 
_ that will develope other cells similar to them- 
selves, just as it is an ultimate fact in physics 
that masses of matter attract each other ; or in 
chemistry, that the molecules of different sub- 
_ Stances have a tendency to unite, so as to form 
_ a compound different from either of the ele- 
ments. It is of such ultimate facts that the 
_ Science of vitality essentially consists. The 
_ conditions under which the assimilating power 
_ Operates are, however, like the laws of chemical 
affinity, freely open to our investigation ; and 
it is a great step in the progress of the inquiry 
_ to become aware that these are so closely con- 
formable throughout the organized world, as 
_ we have endeavoured to show them to be. 
_ It may be stated as a general fact, that in 
assimilating or converting into its own sub- 
_ stance matter which was previously unable to 
_ exhibit any of the manifestations of life, every 
- cell thereby participates in the process of orga- 
nization and vitalization ; for by the new cir- 
cumstances in which the matter is placed its 
sensible properties are altered,—some which 
were previously dormant being now caused to 
manifest themselves, whilst others, which were 
‘previously evident, become latent. No mat- 
a that is not in a state of organization can 
exhibit these properties, which, from their being 
peculiar to living bodies, and altogether diffe- 
rent from those of which physics and chemistry 
take cognizance, are termed vital ; and it may 
also be asserted that no matter which exhibits 
perfect organization is destitute of the peculiar 
vital properties belonging to its kind of struc- 
ture. (See Lire.) Hence every act of nutri- 
tion is, in fact, the creation of a new amount of 
_ vital force ; and when that vital force has been 
_ expended, no more can be developed except by 
the nutritive process. 
_ From the foregoing details it further results 
that we must regard each part of the organism 
as having an individual life of its own, whilst 
contributing to uphold the general life of the 
entire being. This life, or state of vital action, 
ends upon the due performance of the func- 
tions of all the subordinate parts which are 
osely connected together. The lowest classes 
of organized beings, and even the highest at 
| an early stage of their embryonic developement, 
are made up of repetitions of the same ele- 
| ments; and each part, therefore, can perform 
if ts functions in great degree independently of 
‘the rest. But in ascending the scale or in 
tracing the advancing developement of the em- 
‘bryo, we find that the individual lives of the 
¢ells become gradually merged (so to speak) in 
the general life of the structure; for they be- 
come more and more different from each other 
in function, and therefore more and more de- 
| pendent on each other for their means of sup- 
ons 3 So that the activity of all is necessary for 
the maintenance of any one. Hence the inter- 
Tuption of the function of any important organ 
, 
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757 
is followed by the death of the entire structure; 
because it interferes with the elaboration, circu- 
lation, and continual purification of that nutri- 
tious fluid which supplies she pabulum for the 
growth and reproduction of the-individual cells. 
But their lives may be prolonged for a greater 
or less duration after the suspension of the 
regular series of their combined actions ; hence 
it is that molecular death is not always an im- 
mediate consequence of somatic death. (See 
Deatu.) Butif the function of the part have 
no immediate relation to the indispensable 
actions just referred to, it may cease without 
affecting them; so that molecular death may 
take place to a considerable extent without 
somatic death necessarily resulting. 
The foregoing considerations have a very 
important bearing on the question of the de- 
gree to which the process of nutrition is under 
the influence of the nervous system, a question 
on which, as it appears to the writer, very erro- 
neous ideas have been commonly entertained. 
For it has been customary to speak of this pro- 
cess (as well as of secretion) as dependent upon 
nervous agency; or, in other words, to assert 
that the nervous system is not only the instru- 
ment of the functions of animal life, but is also 
the primum mobile of the organic operations. 
Now the independent properties of the cells in 
which all organized tissues originate, might be 
of itself a satisfactory proof that in animals, as 
in plants, the actions of nutrition are the results 
of the powers with which they are individually 
endowed; and that whatever influence the 
nervous system may have upon them, they are 
not in any way essentially dependent upon it. 
Moreover there is an evident improbability in 
the idea “that any one of the solid textures. of 
the living body should have for its office to 
give to any other the power of taking on any 
vital actions;” and the improbability becomes _ 
an impossibility, when the fact is known, that 
no formation of nervous matter takes place in 
the embryonic structure, until the processes of 
organic life have been for some time in active 
operation. The influence which the nervous 
system is known to have on the function of 
nutrition may operate in several ways. Thus, 
if the nerves proceeding to any set of muscles 
be divided, those muscles will be atrophied in 
consequence of the cessation of their activity, 
as already explained. In other instances we 
may not improbably regard the influence of the 
nervous system to be exercised through the 
medium of its controlling power over the dia- 
meter of the bloodvessels, by which it may 
govern the afflux of blood. And there can be 
little doubt that, in some manner yet unex- 
plained, the nervous system exerts an influence 
over those preliminary processes, by which the 
plastic element of the blood is elaborated; so 
that long-continued anxiety or depression of 
mind may produce general atrophy, or a ten- 
dency to tuberculous deposit. It appears to 
be invariably through emotional states of the 
mind that the nutritive process is affected ; the 
will not possessing any direct power of influ- 
encing them. But there can be no doubt that 
the continual voluntary direction of the atten- 
