594 OF NUTRITION. 



Fibrine, a substance which possesses a tendency to spontaneous organization, 

 and which must be regarded as endowed with Vital properties. It is convenient 

 to speak of it, therefore, under a distinct designation ; and the term Assimilation 

 has been applied to it. In its more restricted sense, the term Nutrition is 

 applied to the growth of the various tissues of the body, at the expense of the 

 materials prepared by the Assimilating process, and supplied by the Circu- 

 lating current. 



782. It appears evident, from what has been formerly stated (Chap, in.), 

 that the process of Nutrition mainly consists in the growth of the individual 

 cells composing the fabric; and that these derive their support from the 

 organic compounds with which they are supplied by the blood, just as the 

 cells composing the simplest Plants derive theirs from the inorganic elements 

 which surround them. And as different species of the latter select and com- 

 bine these in such modes and proportions as to give rise to organisms of 

 very diversified forms and properties, so is it easily intelligible that the dif- 

 ferent parts of the fabric of the highest Animals should exercise a similar 

 selective power, in regard to the materials with which the blood supplies 

 them. The structure composing every separate portion of the body has 

 (what may be termed) an elective affinity for some particular constituents of 

 the blood ; causing it to abstract from that fluid, and to convert into its own 

 substance, certain of its elements. The property by which the cells of the 

 Animal or Vegetable structure are enabled to perform it, is one of which we 

 are not likely soon to know more. It will probably long remain an ultimate 

 fact in Physiology, that cells have the power of growing from germs, of under- 

 going certain transformations, and of producing germs that will develope other 

 cells similar to themselves ; just as it is an ultimate fact in Physics, that 

 masses of matter attract each other; or in Chemistry, that the molecules of 

 different substances have a tendency to unite, so as to form a compound dif- 

 ferent from either of the elements. It is of such ultimate facts as these, that 

 the science of Vitality essentially consists : since the Physical and Chemical 

 phenomena which occur in living bodies, are not strictly removable from the 

 laws of Inorganic Nature. The conditions under which this appropriating 

 power operates, however, are 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 conformable, throughout the organized world, as they have been 

 shown to be. It may be stated, as a general fact, that in assimilating, or con- 

 verting into its own substance, matter which was previously unable to exhibit 

 any of the manifestations of life, every cell thereby participates in the process 

 of organization and vitalization; for, by the new circumstances in which the 

 matter is placed, its properties undergo a change, or, to speak more correctly, 

 properties which were previously dormant are caused to manifest themselves. 

 No matter, that is not in a state of Organization, can exhibit those properties, 

 which, from their being peculiar to living bodies, and altogether different from 

 Physical and Chemical, 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 structure.* As a corollary to this 

 general fact, it may be stated, that no organism can be produced by any 

 fortuitous combination of inorganic matter; since, even for the generation of 

 the simplest cell, there is required a cell previously existing, to furnish the 

 germ. 



* Fora fuller consideration of this question, and the grounds upon which this view is 

 supported, the reader is referred to the Article Life in the Cyclopedia of Anatomy and Phy- 

 siology; and to the Chapter on the ''Nature and Causes of Vital Actions," in his 1'riuciples of 

 General and Comparative Physiology. 



