14 The Mechanistic Conception of Life 



We therefore see that the process of the activation of 

 the egg by the spermatozoon, which twelve years ago was 

 shrouded in complete darkness, is today practically com- 

 pletely reduced to a physico-chemical explanation. Con- 

 sidering the youth of experimental biology we have a right 

 to hope that what has been accomplished in this problem will 

 occur in rapid succession in those problems which today still 

 appear as riddles. 



V. NATURE OF LIFE AND DEATH 



The nature of life and of death are questions which 

 occupy the interest of the layman to a greater extent than 

 possibly any other purely theoretical problem; and we can 

 well understand that humanity did not wait for experimental 

 biology to furnish an answer. The answer assumed the 

 anthropomorphic form characteristic of all explanations of 

 nature in the prescientific period. Life was assumed to begin 

 with the entrance of a ''life principle" into the body; that 

 individual life begins with the egg was of course unknown to 

 primitive or prescientific man. Death was assumed to be 

 due to the departure of this ''life principle" from the body. 



Scientifically, however, individual life begins (in the case 

 of the sea-urchin and possibly in general) with the accelera- 

 tion of the rate of oxidation in the egg, and this acceleration 

 begins after the destruction of its cortical layer. Life of 

 warm-blooded animals — man included — ends with the cessa- 

 tion of oxidation in the body. As soon as oxidations have 

 ceased for some time, the surface films of the cells, if they 

 contain enough water and if the temperature is sufficiently 

 high, become permeable for bacteria, and the body is 

 destroyed by micro-organisms. The problem of the begin- 

 ning and end of individual life is physico-chemically clear. 

 It is, therefore, unwarranted to continue the statement that 

 in addition to the acceleration of oxidations the beginning of 



