PHYSIOLOGICAL 329 



The past century's synthetic achievements of the organic chemists, 

 as from Wohler's production of urea in 1828 to Fischer's sugars 

 and more in current progress, have long appeared to support the 

 mechanistic philosophy of life. But here Bergson and Johnstone 

 reply that such marvels are after all but fresh examples of man's 

 best functioning as regards Nature ; in which — despite an industrial 

 age characterised by the so-called "development" of natural regions, 

 but too largely a dissipation of their energies — he is now beginning 

 to return to his normal human and even organic task, that of the 

 reaction of life against the physical running down of the Universe 

 towards maximum entropy. 



That such a termination for the entire L^niverse is not entirely 

 to be feared, is argued from the fact that as the astronomer (on 

 the large scale, if not this solar and planetary one) can conceive of 

 no beginning, but only of the past as practically (if not speculatively) 

 eternal, this conclusion of its activities should already have arrived, 

 were there not also in the Universe a compensatory process — 

 somewhere and somehow — though as yet he knows not where, nor 

 how. It is thus something encouraging and suggestive towards future 

 inquiry, that — albeit within the small planetary experience to which 

 we are in this respect so strictly limited — we should find in the 

 processes by which organic life sustains itself (and even in the 

 experimental syntheses in detail which we are learning to accom- 

 plish), some clear evidence that the reversibility of the general 

 dissipation and degradation of energy is conceivable; since here, 

 on our small world, we see it on a scale sufficient to sustain the 

 activities of life; indeed, even characterising them. 



THE CIRCULATION OF NITROGEN.- Living matter always 

 contains a mixture of proteins, which are complex nitrogenous 

 carbon compounds. It follows that there must be nitrogen in the food. 

 Animals get their nitrogen supplies by eating other animals or from 

 vegetable food. Plants get their nitrogen supplies from nitrates and 

 the like in soil. The nitrates and other nitrogenous compounds in 

 the soil are due to the action of nitrifying bacteria which work on 

 the ammonia that results from the decomposition of decaying 

 organic matter or from the waste-products of animals. The bacteria 

 in question oxidise the ammonia into nitrous and nitric acids which 

 plants can utilise. There are other denitrifying bacteria, however, 

 that break up nitric and nitrous acids and return the nitrogen to 

 the immense stock that there is in the atmosphere. This atmospheric 

 nitrogen may be captured and fixed in natural conditions by electric 

 discharges, as in thunderstorms, or by the quiet and rather mysteri- 

 ous work of certain bacteria that live in partnership with various 

 kinds of plants, especially those of the pea and clover order 

 (Leguminosae). So a nitrogen-circle may be like this: Atmospheric 



