232 NUTRITION OF CELLS. 



cell are straight and run parallel to one another to the 

 point where they diverge in opposite directions. See " Phil. 

 Trans.," 1863. 



THE NUTRITION AND INCREASE OF CELLS. 



On the Nutrition of a Living Cell. In nutrition, the 

 active changes are exclusively confined to the bioplasm. 

 The formed material which has been produced is passive, 

 and probably acts like a filter, permitting some things to 

 pass and interfering with the passage of others. In nutri- 

 tion, pabulum becomes bioplasm, and thus the bioplasm 

 which has been converted into formed material is replaced. 

 But let us consider the order in which these changes occur, 

 and let us try to express them in the simplest possible 

 manner. 



The bioplasm which came from pre-existing bioplasm may 

 be called a; the non-living pabulum, some of the elements 

 of which are about to be converted into bioplasm shall be 

 b; and the non-living formed material resulting from 

 changes in the bioplasm, c. 



It is to be remarked that b does not contain c in solu- 

 tion, neither can c be made out of b unless b first passes 

 through the condition a, and a cannot be formed artificially, 

 but must come from pre-existing a. In all cases b is trans- 

 formed by a into a, and a undergoes conversion into c. 



Can anything be more unlike chemical and physical 

 change? Neither a, nor b, nor c can be made by the 

 chemist ; nor if you give him b can he make a or c out of 

 it ; nor can he tell you anything about the " molecular con- 

 dition " or chemical constitution of a, for the instant he 

 commences to analyse a, it has ceased to be a. He is 



