200 AIR AND LIFE. 



40,000 and 80.000, while at 7,000 meters altitude, and above the sea at 

 some distance from the shore, none at all are found. These figures are 

 enough to show how the air under certain circumstances is a dangerous 

 agent, and serves as a vehicle of death. 



As we have seen, air is fraught with life as well as with death. Each 

 of its constituents is essential to life, and each is also a cause of death. 

 The one that appears to be the most vivifying of them all, becomes uuder 

 certain conditions and doses, a fatal poison; the most useless, the most 

 harmful is, when carefully investigated, an essential basis of the whole 

 structure of life. And the general conclusion is that none could disap- 

 pear, none could exist under a different form or in markedly different 

 proportions, without soon altering the features of our planet and chang- 

 ing it into a naked and barren globe on whose surface no living being, 

 of the present type, could be found. 



If we study the subject more attentively we become aware of another 

 fact. We perceive, to use again J. B. Dumas's very happy phrase, 

 that all living beings are, at last analysis, nothing but condensed air, 

 Plants exist mainly by reason of the existence of air, and animals and 

 man can not exist without plants. The elements of plants are air, 

 and animals live upon plants; the connection is direct and intimate, 

 and man, therefore, is also only condensed air. And as this air, since 

 the centuries during which mankind has existed, has been unceasingly 

 migrating from generation to generation, from individual to individual, 

 now part of some of our human ancestors, later returning to the atmos- 

 phere, and thus perpetually pursuing its cycle, our present organism is 

 made of the same elements as that of our ancestors. Their substance 

 is also ours. And this substance, which is also that of past animals and 

 plants, goes on through space as an untiring wave. To-day or to-mor- 

 row a flower or a fruit, it will unite at one time to form a portion of a 

 sluggish mollusk, at another to help build the brain of a Descartes, a 

 Newton, a Pascal, a Shakespeare, a Helmholtz, a Joan of Arc. The 

 cycle is never interrupted. No human eye witnessed its beginning; 

 none will witness its end. It seems to be infinite and eternal — 

 although, doubtless, it is neither — and alternating from life to death, as 

 old as the world and yet as young as the newborn; if consciousness 

 were among its attributes it would have gone through all that life 

 may give — the highest joys, the deepest sorrows, and all emotions, the 

 noblest as well as the basest. 



The breeze which gently moves the leaves, the wind which moans 

 through the high forests, is the sum total of all life that has been. It 

 is the material of all that has had existence, of those that came before 

 us, of those that are no more and for whom we weep. JSTow it becomes 

 part of ourselves and to-morrow, perhaps, it will go on, pursuing its 

 way, unceasingly metamorphosed from organism to organism without 

 choice or favor, according to law, till the time comes when our globe, 

 no longer heated by the cooling sun, shall slowly die. Then all the 



