478 GENERAL PHYSIOLOGY 



occur in the living cell proteids, carbohydrates and fats, in other 

 words, the three chief groups of organic compounds, and likewise 

 the products of their decomposition ; in brief, there occur all the 

 essential substances that are found in the dead cell. 



There remains only the question whether, in addition, com- 

 pounds exist in the living substance which are destroyed at death 

 and hence are not to be found in the dead cell. A comparison of the 

 chemical behaviour of living and dead cell-substance forces us to as- 

 sume the existence of such compounds. Physiological chemistry 

 has shown that between the two kinds of substance very essential 

 chemical differences exist, which prove that living substance ex- 

 periences in dying pronounced chemical changes. A wide-spread 

 difference between the two consists in their reaction. The re- 

 action of living substance is almost without exception alkaline or 

 neutral and with death changes usually to acid. Further, certain 

 proteids that are in solution in living cell-substance, as, e.g., the 

 myosin of muscle, experience very remarkable changes. In death 

 they coagulate and pass into the solid state, which is very unfit 

 for further chemical transformations. Physiological chemistry has 

 shown similar changes in death in great number. All these facts 

 prove that in the death of living cell-substance certain chemical 

 compounds undergo transformations ; hence substances exist in it 

 which are not to be found in dead cell-substance. 



The fact that these chemical compounds are only present in the 

 living substance and are decomposed with death necessitates the 

 conclusion that the vital process is associated very closely with 

 their existence. At all events an important property belonging to 

 them is their great inclination toward transformation, which is for 

 life an indispensable element. When it is borne in mind how few 

 causes are able to produce death, how almost all chemical sub- 

 stances that are at all soluble in water enter into chemical relations 

 with living cell-substance, while dead cell-substance usually be- 

 haves wholly indifferently to the same influences, it must be said 

 that the substances that distinguish living from dead cell-substance 

 possess a very loose constitution. 



This conclusion is still more obvious when the fact of metabolism 

 is considered. Metabolism shows that the living cell-substance is 

 being continually broken down and reformed, this process being 

 made possible by the continual giving-off and taking-in of 

 material. In contrast to this, under favourable conditions, dead 

 cell-substance is capable of preservation for an extraordinarily long 

 time without its excreting more than a trace of the material that 

 living cell-substance gives off continually. Hence, in contrast to 

 the former, the latter must be distinguished by the possession of 

 complexes of atoms that have very great tendency toward chemical 

 transformations and are continually undergoing self-decomposition. 

 The great lability of these complexes depends upon the fact that 



