342 THU POPULAR SCIENCE MONTHLY. 



ulum to vegetable life." This was but the next year after Priestley's 

 discovery of oxygen itself; yet to this day there lingers in our com- 

 mon thought an undefined impression that the carbonic acid of the 

 air is just an impurity, tolerated because there is only a little of it, 

 but an impurity that it were as well to be rid of altogether. Now, if 

 the redundant resources of life were at our human disposal, we might 

 be in danger, some day, in the sheer forgetfulness of self-regard, of 

 throwing away as an impurity the very foundations of sustenance. 

 Some one, perhaps, would set forth that this gas when not diluted is 

 immediately fatal to human life ; another woixld declare, " Once a poi- 

 son, always a poison ; " and another would ask why we should imperil 

 our own health for the sake of the plants. 



Oxygen was named next, among the primary resources, redundant 

 in supply. It is a prominent constituent of all living tissues, forming 

 seventy-two parts in a hundred of the human body with its fluids. It. 

 is taken in two conditions : first, in combination, chiefly by the j^lants ; 

 second, iu the elemental state, by animals. In combination, it is taken 

 by the plants from carbonic-acid gas, just noticed as a source of car- 

 bon ; from Avater, to be considered as a source of hydrogen ; and, in 

 smaller quantities, from a considerable number of other substances. 

 The greater part of the oxygen in animal tissues is obtained in the 

 products elaborated by the plants. 



But for all animal life the most imperative demand is for oxygen 

 in the elemental state. 



The other elemental resources are available only in their com- 

 pounds; oxygen does its best service when alone. The others serve 

 life as materials for its bodily tissues ; oxygen has an additional duty, 

 the maintenance of operations giving warmth and strength. The 

 activities of life consume various materials, but most constantly of all 

 they demand a raw material of inorganic nature, a simple material in 

 its primitive condition. This supply of elemental oxygen, a necessity 

 for all animal life, is a necessity that is imminent in direct proportion 

 to vital activity, and for man is absolutely imperative. When supplied 

 with oxygen, we can subsist days without other food ; when deprived 

 of oxygen, life fails in a few minutes. It is scarcely a figure of speech 

 to say that the breath is the life. The energy of oxygenation is told 

 in every stroke of the heart. The food that is eaten does not raise an 

 iota of bodily strength without the help of the pound and a quarter 

 of pure oxygen that is daily inhaled. To breathe poorly is to faint ; 

 to eat richly and breathe poorly is to sufibcate and perish. 



The supply of elemental oxygen is certainly impartial and bountiful 

 without reservation. It is more than given it is pressed upon us ; to 

 escape from it is a work of toil and difiiculty. No one is poor from 

 want of it, or rich from gain of it. Were it furnished for pay, all 

 that a man hath would he give for an hour's supply of it. The poor, 

 taken together, fare best in its use; while the wealthy, in their elabo- 



