34 LIVING MATTER OR PROTOPLASM. 



tains two free elements, sulphur and carbon, and one compound, 

 saltpetre or nitrate of potassium (K!N"O 3 ). Saltpetre is an unstable 

 compound, the nitrogen, oxygen and potassium being loosely 

 combined. When heat is applied in the form of a spark the 

 oxygen is released from its feeble union and suddenly combines 

 with the carbon and sulphur to form stabler compounds- namely, 

 carbon dioxide (CO,), monoxide (CO), etc. the nitrogen being 

 more or less completely set free. In other words, the strong 

 affinities of oxygen for carbon and sulphur are satisfied at the 

 expense of its weaker affinities for potassium and nitrogen, the 

 result being a sudden liberation of energy which produces the ex- 

 plosion. Again, nitro-glycerine is a very complex compound, 

 C 3 H 5 O 3 (NO 2 ) 3 , in a state of unstable equilibrium ; that is, its 

 elements are bound together by weak affinities which may readily 

 be overcome. A sudden shock, such as a blow, causes an 

 instantaneous and violent re-arrangement of the elements of 

 the molecule into a number of simpler and stabler molecules 

 (CO 2 , CO, H 2 O, K, etc.). Here, again, strong affinities, held in 

 check under ordinary conditions, are suddenly satisfied at the ex- 

 pense of weaker affinities, and an enormous amount of energy 

 is set free.* 



Something of this sort we must picture to ourselves as taking 

 place in living matter. Protoplasm takes in various complex 

 food-matters and absorbs free oxygen. These substances are built 

 up into the living fabric where they are loosely united to form 

 unstable or explosive compounds containing a large amount of 

 potential energy. By the timely and orderly explosion of these 

 compounds, under nicely regulated conditions, their potential 

 energy is converted into kinetic energy which manifests itself as 

 the so-called vital force underlying every vital act. Apart from 

 the phenomena of consciousness, vital actions thus cpnceived lose 

 much of their supposed mysterious and unfathomable character; 

 for "vital force'' is not a unique and isolated power, but a 

 form of physical energy derived from and convertible into other 

 well-known forces of nature. 



The foregoing considerations lead directly to an account of 

 the chemical composition of living matter. 



* According to Berthelot, the reaction is as follows : 2C a H 5 O 3 (NO 2 ) 3 = 



