THE PROCESS OF EXCITATION 95 



stance, the hydrogen atoms loosely combined with carbon enter 

 into strong combinations with oxygen and the oxygen loosely 

 combined with the nitrogen enters into strong combination with 

 carbon, so that water and carbon dioxide are formed and nitrogen 

 and oxygen set free. 



/H /H 



C-H CrH ^ 



0-N^o 



H 



/ 



H 



= 5H 2 0+6C0 2 +3N 2 +0 



In the functional disintegration of living substance, the last 

 type is realized. Living substance contains loose complex com- 

 binations, and we know that functional disintegration is accom- 

 panied by the consumption of these organic combinations. In 

 the functional disintegration of muscle substance the nitrogen- 

 free groups are concerned, and we must, consequently, first con- 

 sider the carbohydrates. However, without further study we 

 should not generalize from that which is true in the case of 

 muscle. There are other forms of living substances which con- 

 tain different combinations, which disintegrate as a result of the 

 contact of a stimulus and yield carbon dioxide. A clue as to 

 which combinations in individual cases undergo disintegration 

 as a result of excitating stimulation, is furnished by the metab- 

 olism of rest in the particular substance. Plants and micro- 

 organisms have been investigated more thoroughly in this con- 

 nection than animals. Plant physiology has demonstrated that 



