41() THE LIFE OF MATTER. 



caut^es it to pass through all .states of coloration before redueiiio- it; 

 the salt stops at the state which protects it best. It stops at red, if it 

 is red light that assails it, because by becoming- red it repels by reflec- 

 tion, that light; that is to say, it absorbs it the least. 



It ma}^ then be advantageous, for the purpose of comprehending 

 natural phenomena, to regard the transformations of inanimate matter 

 as manifestations of a sort of internal life. 



Conclusion — Rdations of the Hurro'Widbuj nicdhnu to tlic I i ring 

 7)('/' /if/ 0)id f/te hri/fehodj/.— Brute f)odies then are not imnuitable any 

 more than are living bodies. Both depend upon the medium that 

 surrounds them, and they depend upon it in the same way. Life 

 brings together, puts in conflict, an appropriate organism and a suita- 

 lf)le environment. Auguste Comte and Claude Bernard have taught 

 us that vital phenomena result from the reciprocal action of these two 

 factors Avhich are in close correlation. It is also from the reciprocal 

 action of the environment and the brute body that inevitably i-esultthe 

 phenomena which that body presents. The living body is sometimes 

 more sensitive to ambient variations than is the brute body, but at 

 other times the reverse is the case. For example, there is no living 

 organism as impressionable to any excitant whatever as is the bolometer 

 to the slightest variations of temperatui-e. 



There can only be, then, one chemically immutable body, which is 

 the atom of a simple bod}-, since according to its very definition it 

 remains unaltered and unalterable in combinations. This notion of an 

 unaltera])le atom has, however, itself been attacked l)y the doctrine of 

 the ionisation of particles advanced by J. J. Thomson; and })esides, 

 with very few exceptions — those of cadmium, mercury, and the gases 

 of the argon series — the atoms of simple ])()dies can not exist in a free 

 state. 



So it is that, as in the vital struggle, the ambient medium furnishes 

 to the living being, in whole or in part by alimentation, the materials 

 of its organization and the energies which it puts in play. It also 

 furnishes to brute bodies their materials and their energies. 



It is also said that the ambient medium furnishes the living l>eing a 

 third class of things, the stinmlants of its activities — that is to say, its 

 "provocation to action." The protozoan flnds in the aquatic environ- 

 ment which is its habitat the stimulants which provoke it to move and 

 to absorb its aliments. The cells of the metozoan enccmnter in the 

 same way in the lymph, the blood, and the interstitial li(juids which 

 bathe them the shock, the excitation which brings their energies into 

 pl:iy. They do not have in themselves, by a mysterious spontaneity 

 without example in the rest of nature, the ca|)ri('ious principle which 

 sets them in motion. 



Vital spontaneity, so readily admitted by persons ignorant of biology, 

 is disproved by all the history of the science. Ever}' vital manifesta- 



