LIFE AND LIVING BEINGS 3 



constitution during every moment of its existence, — it is this 

 change which constitutes the process of senile involution. 

 The substance of the child is other than that of the ovum, 

 and the substance of the adult is not that of the child. Hence 

 we cannot regard nutrition as the exclusive characteristic 

 of life. 



Other authorities regard growth and organization as the 

 essentials of life. But crystals also grow. It was said that the 

 growth of a crystal differed from that of a living thing, in that 

 the former grew by the addition of material from without — 

 the juxtaposition of bricks, as it were — while the latter grew by 

 intussusception, an introduction of fresh material into the 

 substance of the organism. A crystal, moreover, was homo- 

 geneous, while the tissues of a living being were differentiated 

 — such differentiation constituting the organization. At the 

 present time, however, we recognize the existence of a great 

 variety of purely physical productions, the so-called "osmotic 

 growths," which increase by a process of intussusception, and 

 develop therefrom a marvellous complexity of organization and 

 of form. Hence growth and organization cannot be considered 

 as the essential characteristics of life. 



Since, then, we are totally unable to define the exact 

 boundary which separates life from the physical phenomena of 

 nature, we may fairly conclude that no such separation exists. 

 This is in conformity with the "law of continuity," — the 

 principle which asserts that all the phenomena of nature are 

 continuous in time and space. Classes, divisions, and separa- 

 tions are all artificial, made not by nature but by man. All 

 the forms and phenomena of nature are united by insensible 

 transition; it is impossible to separate them, and in the 

 distinction between living and non-living things we must 

 content ourselves with relative definitions, which are far from 

 being precise. 



Life can only be defined as the sum of all phenomena 

 exhibited by living beings, and its definition thus becomes 

 a mere corollary to the definition of a living being. 



The true definition of a living being is that it is a trans- 

 former of energy, receiving from its environment the energy 



