THE DEFINITION OF LIFE. 



523 



are produced in the green leaves of plants by the 

 union of carbon and water under the influence of 

 the sun, are really very well-marked chemical 

 phenomena. If the synthetical processes are much 

 less clear in the instance of azoted or albuminoid 

 matters, the reason is, that organic chemistry is 

 not yet far enough advanced to explain them ; 

 but it is very certain, nevertheless, that these sub- 

 stances are formed by chemical processes in the 

 organisms of living beings. It must be owned 

 that the agents of organic synthesis, the germs 

 and cells, may be said to be entirely exceptional 

 agents. It might be said, in the same sense, as 

 to phenomena of disorganization, that ferments 

 are agents special to living beings. In my own 

 view, it is a fact that there is such a general law, 

 and that chemical phenomena are made to occur 

 in the organism by special agents or processes ; 

 but that fact does not at all affect the purely 

 chemical nature of the phenomena that take place, 

 and of the products that result from it. 



After this study of chemical synthesis, let us 

 take organic evolution. The agents of chemical 

 phenomena in living bodies do not stop with pro- 

 ducing chemical syntheses of exceedingly various 

 substances, but go on to organize them and apply 

 them to the morphological construction of the new 

 being. The most potent and wonderful among 

 these agents of living chemistry is unquestiona- 

 bly the egg, the primordial cell that contains the 

 germ, the organizing principle of the whole body. 

 We are not present at any creation of the egg ex 

 nihilo : it comes from the parents, and the origin 

 of its virtue of evolution is hidden from us ; but 

 science is ascending nearer to this mystery every 

 day. It is by the germ, and by reason of that 

 kind of power of evolution it possesses, that the 

 perpetuity of species and the descent of beings 

 are established ; by it we understand the neces- 

 sary relations existing between the phenomena of 

 nutrition and those of development. It explains 

 for us the limited duration of the living being, for 

 death must come when nutrition stops, not because 

 aliment fails, but because the developing progress 

 of the being has reached its end, and the cell's 

 impulse of organization has exhausted its virtue. 



Again, the germ directs the organization of 

 the being, by forming living substance with the 

 aid of surrounding matter, and by giving it those 

 qualities of chemical instability which become the 

 cause of the unceasing vital movements that take 

 place in it. The cellules, those secondary germs, 

 in the same way govern the nutritive cellular or- 

 ganization. It is very clear that these are purely 

 chemical acts ; but it is not less plain that these 



chemical acts, in virtue of which the organism 

 increases and builds up, follow in linked succes- 

 sion with a view to this result, which is, the or- 

 ganization and the growth of the individual, 

 whether animal or vegetable. There is, as it were, 

 a scheme of life, which sketches the plan of every 

 being and of every organ ; so that if, considered 

 by itself, each phenomenon of the organization 

 depends on the general forces of Nature, yet. 

 taken as a whole, and in their succession, these 

 phenomena seem to disclose a special bond among 

 them ; they seem to be guided by an unseen con- 

 ditioning something in the course they follow 

 and in the order that holds them together. Thus, 

 the chemical synthetic acts of organization and 

 nutrition come to view as if they were ruled by 

 an impulsive force governing matter, working 

 with a chemistry applied to an end, and bringing 

 together the laboratory's senseless reagents, as the 

 chemist himself does. That force of evolution, 

 imminent in the ovule which is to reproduce a 

 living being, unites within it, as we have explained, 

 the phenomena of generation and of nutrition; 

 both, therefore, have an unfolding character, 

 which is their basis and essence. 



It is this evolutive power, or property, which 

 we now merely designate, that alone could com- 

 pose the quid proprium of life, for it is certain 

 that this evolutive property of the egg which will 

 produce a mammal, a bird, or a fish, belongs nei- 

 ther to physics nor to chemistry. The theories 

 of the vitalists cannot, at this day, hover over the 

 whole field of physiology. The evolutive power 

 of the egg and the cells is thus the last stronghold 

 of vitalism ; but, in taking refuge there, it is easy 

 to see that vitalism changes into a metaphysical 

 conception, and breaks the last tie that bound it 

 to the physical world, or to physiological science. 

 When we say that life is the guiding idea, or the 

 evolutive force of the being, we merely express the 

 thought of a unity in the succession of all the 

 morphological and chemical changes effected by 

 the germ, from the beginning to the end of life. 

 Our mind grasps that unity as a conception it can- 

 not escape from, and explains it by " a force;" 

 but the mistake is in supposing that this meta- 

 physical force acts after the manner of a physical 

 force. That conception does not quit the region 

 of mind, to react in presence upon those phenom- 

 ena for the explanation of which the mind has 

 formed it; though it issues out of the physical 

 world, it has no retroactive effect upon that world. 

 In a word, the metaphysical evolutive force by 

 which we may describe life is useless to science, 

 because, being outside of physical forces, it can 



