pear to exist, for a time, simply at particular spots of the vascular 

 system. 



The attractions by which living cells thus appropriate to them- 

 selves portions of contiguous fluids, are obviously analogous to those 

 by which even inorganic porous substances attract different fluids 

 with different degrees of force, and thereby produce the phenomena 

 of endosmose and exosmose, but are broadly distinguished from them 

 by the peculiarity of the changes thus effected, by their infinite 

 variety, even in different parts of the same structure, and by their 

 uniformly temporary existence. 



II. The actual transformations, or new arrangements of the che- 

 mical elements which take place in living bodies, and are peculiar 

 to them, are illustrated by the examples of the formation of starch 

 from water and carbonic acid, oxygen escaping ; and of the forma- 

 tion of fat from starch, carbonic acid and water escaping. 



It appears to be in the cells of organized structures that those 

 transformations are likewise effected ; and as the action of cells in 

 simply extracting portions of the nourishing fluid, is analogous to 

 the physical principle of endosmose, so their action in these meta- 

 morphosis may be illustrated, but by no means explained, by com- 

 paring them to those chemical actions to which the term catalysis is 

 applied. 



Two general observations may be made on both these modifica- 

 tions of the power of vital affinity, — first, that they obviously trans- 

 ferred from the portions of matter already endowed with them, to 

 those which, in the growth of living beings, are added to, or substi- 

 tuted for, those portions of matter ; just as muscular fibres already 

 existing, communicate to all the matter which is added to them by 

 the process of nutrition, the same contractile properties which they 

 themselves possess ; secondly, that every portion of matter to which 

 any such vital properties are imparted, appears to enjoy them only 

 for a short time ; losing them so rapidly that a vital process of ab- 

 sorption and excretion is necessary, throughout the whole existence 

 at least of animals, to eliminate from their bodies materials which 

 have lost these properties and reverted to the condition of dead 

 matter. 



After stating these general principles regarding vital affinities, the 

 author made some more special remarks on the most fundamental of 

 all the changes in organized beings which may be referied to their 

 action, viz., the formation of starch and its allied compounds from 



