THE AIR AND LIFE. 531 



thnt pis unless they take it from the combination of oxygen with hem- 

 oglobin? Anaerobism is then a characteristic of animal tissues no less 

 than of certain microbes, and yet none of them can dispC^nse with oxygen. 

 There is no life without oxygen; yet, no life with too much oxygen. 

 Such is the conclusion that has bee,n established by actual facts. 



We shall now discuss nitrogen. As may be inferred from its other 

 name, "azote," nitrogen is unfit for the sustenance of life, and any 

 aninuil or plant placed in an atmospliere of nitrogen will die a speedy 

 death. Not that this gas is i)oisonons, for we inhale it in large quan- 

 tities without feeling its intiuence, but it is inert, inefi'ective, neither 

 an agent in — nor a subject for — combustion. It has no share in respir- 

 ation, and it would seem that its only function in the atmosphere is to mit- 

 igate the action of oxygen. Death would soon follow in an atmosphere 

 of oxygen alone, through injury to the lungs and poisoning of the tis- 

 sues, but when mixed with an inert gas the oxygen penetrates the ogau- 

 ism in moderate quantities only. Oxygen is tempered by nitrogen in 

 the same manner as the alcoliol in wine is tem[)ered by water. That 

 is, to be sure, a very useful functjon, but of a negative order. And yet 

 what else can be expected of an inert gas? If however some account 

 be taken of the chemical constitution of living beings and of the 

 abundi'.nce of nitrogen they contain; if also account be taken of the 

 fact that four-fifths of the atmosphere consists of nitrogen and that 

 animals will die when deprived of nitrogenous food, as was shown by 

 Magendie, it would seem that that gas must perform some other more 

 important and active function. Let us take this well established fact 

 for a starting point: Nitrogenous food is indispensable to maintain life 

 in beings of the higi.er orders. How can plants which directly or 

 indirectly provide the nutriment of those beings, lay up a supply of 

 nitrogen? The natural answer is, they take it from the atmosx)here. 

 But how ? 



That question is one that has engrossed the earnest attention of 

 chemists and agriculturists, and in France, notably, Boussingault, 

 Berthelot, Deherain, and George Ville have devoted considerable time to 

 its study. They ascertained that certain plants obtain nitrogen eithe» 

 in the form of nitrates produced by (;ombination of the nitric acid of the 

 air with substances in the soil, or in the form of ammoniacal vapors 

 But M. Berthelot several years ago showed that there was another 

 factor in the problem, tlmt tlie soil doubtless contains microbes endowed 

 with the power of so treating the nitrogen of air that it can be assimi- 

 lated by i>lants. This theory has been fully confirmed by two German 

 scientists, Messrs. Hellriegel and Wilfarth, whose most vahiable inves- 

 tigations have been lecently published. They discovered that certain 

 plants, and especially leguminous ones, possess the property of thriving 

 in soil poor in nitrates, and of taking the requisite quantity of nitrogen 

 from the air by means of special microbes that live on their roots. If 

 the microbes are destroyed, the growth of the plant will be stunted, if 



