32 THE SCIENCE OF LIFE. 



ilar material ; the living tissue takes into its interior ma- 

 terial which it transforms out of pabulum, which is foreign 

 to its own structure, while at the same time it discards 

 such molecules or atoms as are unfit for further use. 



The chemical composition of the various tissues of the 

 body cannot be found in the blood, or pabulum, which 

 nourishes the tissues, but results from metamorphosis, or 

 transformation, by means of the bioplasts. Endosmose, 

 or the physical property by which fluids pass through 

 membranes, or gummy matters, will not account for it, 

 since in the latter there is no change of material, while 

 in nutrition there is rearrangement of the atoms in the 

 tissue-molecules. 



Nutrition has sometimes been compared with crystalli- 

 zation, but crystallization is a deposit of material from a 

 solution of similar substance, and is altogether different 

 from nutrition by transformation and selection. 



Nutrition has also been compared with a chemical 

 phenomenon called catalysis. In this, chemical change 

 takes place because of the presence of a substance which 

 remains itself unaffected, as when spongy platinum in- 

 duces the combination of oxygen and hydrogen gases. 

 In catalysis the third substance neither gives nor takes 

 from the excited body, but in nutrition the living matter 

 itself selects appropriate chemical elements from its pab- 

 ulum, dissolving their former affinities, and recembining 

 them in a manner which no non-living substance can do. 

 There is no third substance present which is known to 

 us, and all the phenomena are peculiar to living matter, 

 or bioplasm. 



4.) Bioplasm can also transmit vital power to its prog- 



