THE GENERAL CONDITIONS OF LIFE 337 



1. External and Internal Causes of Death 



If we start from the fact that life can only arise, and, moreover, 

 must arise, as soon as a certain complex of conditions is fulfilled, 

 the causes of death in their general form are evident ; for death 

 must then take place so soon as the general conditions of life 

 disappear. In accordance with the distinction between external 

 and internal conditions of life, a distinction must also be 

 made between external and internal causes of death, according as 

 death is due to the removal of the external or of the internal 

 vital conditions. 



To examine, first, the external causes of death, the fact does not 

 require detailed consideration that withdrawal of oxj^gen, water and 

 food-stuffs, and, further, exceeding the necessary limits of tempera- 

 ture and pressure, lead to death, except in the case of organisms that 

 under certain conditions pass into the state of apparent death. 

 But these do not include all the external causes of death. All 

 these conditions may be fulfilled and yet death be brought about 

 by the action of external causes. Hence we must reckon among 

 the external conditions of life the absence of such influences as are 

 destructive to living substance, especially chemical and electrical 

 influences. 



The chemical influences that produce fatal effects are the 

 poisons, and they are innumerable. All chemical substances that 

 come into chemical relation with any of the essential constituents 

 of living substance so that the mechanism of metabolism thereby 

 suffers disturbance, cause death, sometimes after very brief, some- 

 times after long-continued action, death following very rapidly or 

 constituting the end of long, necrobiotic changes. If, e.g., mineral 

 acids or metallic salts act upon the living substance of a cell, the 

 cell inevitably dies, because all proteid is precipitated or chemically 

 combined by these substances so that metabolism must cease. 

 Other substances that are poisonous to all living substance are the 

 anassthetics (chloroform, ether, alcohol), the vapours of which by 

 continued action finally bring all vital phenomena to a standstill, 

 whether in plants, animals or unicellular forms.^ To what change 

 of the living substance this peculiar effect of anaesthetics is due 

 is for the present -wholly unknown ; and the same must be said 

 of the great majority of poisons that act, some upon all living 

 substance, and some upon certain cells onlj-. 



Like poisons, electricity in great intensity also acts harmfully to 

 living substance by producing chemical changes in it. It is well 

 known that chemical compounds in solution can be decomposed 

 by a galvanic current. The compounds of living substance are 



> Cf. Bernard (78). 



