THE VITAL PROPERTIES OF THE CELL 127 



the amount of certain poisons which suffices to kill a large living 

 animal." 



In the reconstruction of living substance, or in progressive 

 metabolism, new material is taken up from outside, to replace that 

 which has been used up ; these substances become incorporated 

 and transformed into new chemical combinations. During the 

 execution of this work, more or less heat is rendered latent, and 

 is converted into potential energy ; this latent heat is derived 

 partly from the intramolecular heat, which is released by the 

 process of decomposition, partly, and in the case of plants chiefly, 

 from the vivifying heat of the sun's rays, by means of which 

 a large amount of kinetic energy is conveyed to the organic 

 world, and is converted in the protoplasmic body into potential 

 energy. The substances taken up from outside, and the heat rays 

 from the sun, supply in the last instance the material and energy 

 required for the carrying on of the vital processes of alternate 

 decomposition and reconstruction. 



According to Pfliiger's definition, " The vital force is the intramolecular 

 heat. The highly unstable molecules of albumen, which are built up in the cell 

 substance, and which become decomposed through a splitting up of the 

 molecules carbon dioxide, water, and nitrogenous bodies being chiefly formed 

 becoming continually regenerated and rearranged." 



In spite of the great variety of metabolic processes which occur 

 in a single individual, there is a series of fundamental processes, 

 which are common to all organic bodies, and which take place 

 in the lowest unicellular organisms, as well as in the bodies of 

 plants and animals. Thus the unity of the entire organic kingdom 

 is exhibited in these fundamental processes of metabolism, just 

 as in the phenomena of movement and of reaction to stimuli. 



Up to this point they may be included in the general anatomy 

 and physiology of the cell. This uniformity is especially note- 

 worthy in the following three points : 



1. Each cell, whether plant or animal, respires, that is to say, 

 it is essential to it, to take up oxygen from its environment, by 

 means of which it oxidises the carbo-hydrates and albuminous 

 substances of its own body, and produces as end products carbon 

 dioxide and water. 



2. In both organic kingdoms to a large extent, corresponding 

 substances make their appearance during metabolism, such as 

 pepsin, diastase, myosin, xanthin, sarcin, sugar, inosit, dextrin, 

 glycogen, lactic acid, formic acid, acetic acid, and butyric acid. 



