518 



THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



It is a strange abuse of the term science to ad- 

 mit that vital phenomena cannot be brought 

 under any exact law, any constant and settled 

 condition, and to allow that such phenomena so 

 defined compose a vital science that has the pe- 

 culiarity of being vague and uncertain. There 

 seems to be no reply to be made to such reason- 

 ings, for their very meaning is the want and de- 

 nial of all scientific sense. 



And yet how often has not the same kind of 

 argument been brought forward ; how many doc- 

 tors have maintained that physiology and medi- 

 cine could never be more than half-sciences, sci- 

 ences of conjecture, because we shall never grasp 

 the principle of life, or the hidden character of 

 disease ! These assertions, still echoing in our 

 ears, like the far-off voices of obsolete teachings, 

 have no power to make us pause. Descartes, 

 Leibnitz, and Lavoisier, have taught us that mat- 

 ter and its laws are alike in living bodies and in 

 lifeless substances ; they have shown us that in 

 the world there is but one mechanism, one phys- 

 ics, one chemistry, common to all natural beings. 

 There are not, then, two orders of sciences. 

 Any science worthy to be called so is one which, 

 understanding the exact laws of phenomena, fore- 

 tells them with certainty, and controls them when 

 within its reach. Anything that is wanting in 

 this character is merely quackery or ignorance, 

 for there can be no such thing as half-sciences 

 or conjectural sciences. It is a grave mistake to 

 suppose that in living bodies we have to concern 

 ourselves with the very essence and principle of 

 life. We cannot attain to the principle of any- 

 thing, and the physiologist has nothing more to 

 do with the principle of life than the chemist 

 has with the principle of the affinity of bodies. 

 First causes elude us everywhere, and every- 

 where alike we can reach only the immediate 

 causes of phenomena. Now, these immediate 

 causes, which are nothing else than the very 

 conditions of phenomena, are capable of as rig- 

 orous ascertainment in the sciences of living 

 bodies as in those of lifeless ones. There is no 

 scientific difference among all natural phenome- 

 na other than that in the complexity or delicacy 

 of the conditions under which they appear, mak- 

 ing it more or less difficult to distinguish and 

 define them. Such are the principles that should 

 guide us. Thus, we must unhesitatingly conclude 

 that the duality set up by the vitalist school in 

 the sciences of living and of lifeless bodies is 

 totally opposed to science itself. Unity reigns 

 throughout its domain. The sciences of living 

 bodies and those of inert substance rest upon 



the same principles and must be pursued in 

 study by the same methods of investigation. 



III. 



If vitalist doctrines have come to nothing 

 through the capital error of their principle of 

 dualism or opposition between living Nature and 

 inorganic Nature, the problem always exists. We 

 have to make answer to this eternal question, 

 " What is life ? " or else to the other one, " What 

 is death ? " for the two questions are closely 

 bound together, and cannot be parted. 



The living being has for its essential charac- 

 teristic nutrition. The organic structure is the 

 seat of an unceasing nutritive movement, a secret 

 inward action which leaves no rest for any part ; 

 each, without pause or cessation, feeding itself in 

 the medium that surrounds it, and throwing off 

 into that medium its products and its refuse. 

 This molecular renewal is invisible to direct sight ; 

 but, as we see the beginning and the end, the en- 

 trance and the exit of substances, we imagine 

 their intermediate changes, and we represent to 

 ourselves a flow of matter that perpetually trav- 

 els through the organism, and renews its sub- 

 stance while preserving its form. This move- 

 ment, which has been called the vital torrent, the 

 material circulation between the organic and the 

 inorganic world, exists in the plant as well as in 

 the animal, is never interrupted, and becomes 

 the condition and the immediate cause at once of 

 all other vital manifestations. The universality 

 of such a phenomenon, the constancy it shows, 

 its necessity, make it the fundamental character- 

 istic of the living being, the most general sign of 

 life. There will be no reason for surprise, then, 

 that some physiologists have bean tempted to 

 take it as a definition of life itself. 



This phenomenon, however, is not a simple 

 one ; it is of consequence to analyze it, and pen- 

 etrate more deeply into its mechanism, so as to 

 give exactness to the idea of life we may gain 

 from its superficial observation. The movement 

 of nutrition involves two operations, which are dis- 

 tinct, though inseparably connected : one, that by 

 which inorganic matter is fixed or incorporated 

 into living tissues as an integral part of them ; 

 the other, that by which it releases itself from 

 and quits them. This unceasing twofold move- 

 ment is actually only a perpetual alternation of 

 life and death ; that is, of waste and repair of the 

 component parts of the organism. The vitalists 

 misunderstood nutrition. Some of them, filled 

 with the idea that the essence of life is resist- 

 ance to death — in other words, to physical and 



