THE EXACT MOLECULAR STRUCTURE 21 



in the formation of simpler, oxidized, more stable bodies. The 

 act of dissociation liberates energy, which appears in the mani- 

 festations of life. Pfliiger has suggested that in the change 

 from living to dead protoplasm the cyanogen grouping is 

 converted to the inert ammonia grouping by the absorption 

 of water. It is convenient to designate the expression, mass 

 of living matter, by the shorter terms biogen or bioplasm. 

 By biogen is wider stood the smallest quantity of living matter 

 that can manifest the property of nutrition. 



That part of nutrition designated as metabolism is the most 

 characteristic of all the properties of living matter. By it is 

 meant the total series of changes by which substances are 

 built up into living matter (anabolism) and again broken down 

 (katabolism) . Anabolism and katabolism fiave opposite effects 

 on living matter, but they, nevertheless, go on simultaneously 

 in the same cell, and under normal conditions are always active. 

 When they equal one another the cell is at rest a condition 

 that has been called autonomous equilibrium. If anabolism 

 is in excess of katabolism, the cell increases in bulk or grows, 

 while an excess of katabolism over anabolism will result in 



atrophy. The relations of anabolism to katabolism may be 



^ 

 expressed by the symbol ^r. There is no reason to suppose that' 



biogens are all of the same structure; on the contrary, they 

 are probably as numerous as the cells have different func- 



A 

 tions. Therefore, the relation =- is more correctly expressed as 



---- 2 a - , where each of the factors a v a 2 , 3 . . . 



and d lf d 2 , d 3 , . . . may vary independently of the others, and 

 within very wide limits, as the case may be. 



In any given cell where processes of one kind are in excess 

 over the other a reaction arises which renders the biogen more 

 resistant to further change of the same character, and favors 

 a tendency in the other direction. If, for instance, anabolic 

 changes have been called out in a cell by a stimulus, they 

 generate in time an acceleration of katabolic processes until 

 the two are in equilibrium. The general condition of the cell, 

 however, is above par, and is called allonomous equilibrium. 



