NUTRITION. 



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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- 

 ter 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 LIFE.) 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, 

 depends upon the due performance of the func- 

 tions of all the subordinate parts which are 

 closely 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 

 its 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 

 cells 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- 

 port ; so that the activity of all is necessary for 

 the maintenance of any one. Hence the inter- 

 ruption of the function of any important organ 



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 the 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 

 DEATH.) But if 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 stales 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- 





