INTRODUCTION 



Life was formerly regarded as a phenomenon entirely separated 

 from the other phenomena of Nature, and even up to the 

 present time Science lias proved wholly unable to give a 

 definition of Life; evolution, nutrition, sensibility, growth, 

 organization, none of these, not even the faculty of repro- 

 duction, is the exclusive appanage of life. 



Living thing's are made of the same chemical elements as 

 minerals; a living being is the arena of the same physical 

 forces as those which affect the inorganic world. 



Life is difficult to define because it differs from one living- 

 being to another; the life of a man is not that of a polyp or 

 of a plant, and if we find it impossible to discover the line 

 which separates life from the other phenomena of Nature, it is 

 in fact because no such line of demarcation exists — the 

 passage from animate to inanimate is gradual and insensible. 

 The step between a stalagmite and a polyp is less than that 

 between a polyp and a man, and even the trained biologist is 

 often at a loss to determine whether a given borderland form 

 is the result of life, or of the inanimate forces of the mineral 

 world. 



A living being is a transformer of matter and energy — both 

 matter and energy being uncreateable and indestructible, i.e. 

 invariable in quantity. A living being is only a current of 

 matter and of energy, both of which change from moment to 

 moment while passing through the organism. 



That which constitutes a living being is its form ; for a 

 living thing is born, develops, and dies with the form and 

 structure of its organism. This ephemeral nature of the living 

 being, which perishes with the destruction of its form, is in 



