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tiun of aniuials, to be fewer and simpler than had generally been 

 supposed. 



I. The first kind of action which may be ascribed to vital affinity, 

 he desciibed as the mere selection and retention, by certain portions 

 of a solid, of certain substances, whether elementary or compound, 

 already existing in a fluid that is brought in contact with it, or what 

 is called by some a chemical filtration. This power is exemplified 

 in living vegetables, particularly in the appropriation by them of 

 some of the earthy and saline matters which are brought to their 

 roots, and the rejection of others ; it is more strikingly seen in the 

 development of the lower classes of animals, especially those of the 

 radiata and moliusca, which have horny or earthy integuments ; and 

 it is certainly the chief power concerned in all those functions of 

 animals, to which we give the names of absorption, secretion, and 

 even nutrition. 



In regard to this simplest form of vital affinity, the following 

 points seem ascertained : — 



1. That it is usually, if not always, performed in a perfect or- 

 ganized beinof, by an attractive agency of living or growing cells 

 which seem always to perform the double office of extracting from 

 the nourishing fluid the material of their own growth and reproduc- 

 tion, and extracting also the fluid or solid matter which they are 

 to contain, or with which they are to be incrusted. 



The matters thus consolidated from a fluid in which they pre- 

 viously existed, by a simple process of attraction and inci'eased ag- 

 gregation, not precipitated by any chemical separation of their com- 

 ponent parts, assume the forms peculiar to each organized body to 

 which they are thus added, but retain that peculiarity which in in- 

 organic matter exists only in fluids, — that the smallest portion of 

 them contains all the chemical ingredients which belong to the mass, 

 and thus any crystalline arrangement is prevented. 



2. That no difference, of form or of composition, can be detected 

 in the different cells of an organized structure, to explain the differ- 

 ence of the matters which they thus extract ; and that, in the first 

 development of organized beings, the difference of selecting power 

 exercised at different points of the germinal membrane, appears to 

 be determined by no other condition than their position, — -just as 

 different portions of nervous matter, differing only in anatomical po- 

 sition, exert perfectly different vital powers, oi-, in the state of dis- 

 ease (e.g., of inflammation), peculiar attractions and repulsions ap- 



