58 THE CIRCULATION OF NITROGEN IN NATURE. 
only was the germ not altogether as black as he was painted, 
but that he possessed a vast number of sisters, cousins, 
and aunts, who, so far from being inimical to our well-being, 
were working for our good, and were even indispensable to 
our continued existence. To this second stage succeeded the 
present era of investigation into the mode of action of these 
minute workers, a line of research which bids fair to lead to 
the achievement of the acme of polemical skill — the turning 
the enemy's weapons against himself. 
Our business to-night, however, is with the friendly 
microbes, labouring day and night for the good of all the 
higher forms of life, and more particularly with those 
which, amongst other functions, so manipulate nitrogen and 
nitrogenous compounds as to render them available for the 
maintenance of our life and health. 
But here I must ask your forbearance whilst I briefly 
review such of the chemical relations of nitrogen as are 
essential to the understanding of our subject proper. 
Nitrogen, as you are aware, is a gas constituting by far the 
larger portion — almost exactly four-fifths — of the atmosphere. 
We are therefore dealing with a substance existing in im- 
mense quantities in nature ; for instance, this room contains 
8,424 cubic feet or 626 lb. weight of this gas. I have used the 
name nitrogen because it is that commonly employed ; but the 
great French chemist Lavoisier, who was the first investi- 
gator to show that it was a simple body, called it originally 
azote," meaning inconsistent with life. We now know that 
if there is one element more intimately connected with the 
manifestation of vital force than the others, that element is 
nitrogen. 
Now it has long been known that, besides being a con- 
stituent of air, nitrogen occurs in combination in many 
substances both mineral and organic. 
