504 Proceedings of the Royal Society 
microscopic fungi, in the consideration of which we have been 
engaged, perform a very important function in nature. They form 
a brigade in nature’s army of scavengers. They transform the 
dead matter which once formed part of organised living beings 
into raw materials out of which new organisms construct their 
bodies; they break down the complex substances, when the com- 
plexity has become useless, into simpler compounds which can he 
used again. They demolish the old ruins, and render their stones 
fit to be employed as building materials. But they not only attack 
the dead, they kill the weak and the dying; and while this action 
may be considered useful on the whole, as leaving room for the 
development of the strong, it is precisely the duty of the medical 
man to combat this tendency of nature, to support the weak that it 
may have an opportunity to become strong, to ward off nature’s 
blows that the dying may recover. This is not the place to speak of 
the extraordinary results obtained by Mr Lister’s mode of treatment, 
of the certainty of cure in cases which ten years ago would have 
been considered absolutely hopeless; my object is rather, assuming 
these results, to show how intimately they are connected with the 
scientific truths which form the basis of this mode of treatment. 
It has been suggested, and I confess that I at one time thought 
the suggestion a good one, that instead of trying to convince 
surgeons of the truth of the scientific basis, Mr Lister should draw 
up a code of practical rules which a surgeon might follow without 
thinking of germs or bacteria or fungi. A little consideration will 
show the absurdity of this idea. A surgeon impressed with the 
truth of the scientific basis needs no code of rules — he sees at once 
what he must do, and what he must avoid. A code of rules drawn 
up for one ignorant of the scientific basis would be intolerably 
complicated, and certain to be violated. In this, as in other and 
higher and more general motives, faith is essential to practice; 
if we know the why, we can, as a rule, find out the how; and 
antiseptic surgery will be successful then, and then only, when 
the reasons for its methods are understood and believed in. 
I have endeavoured, Sir, to lay before the Society some of the 
reasons which have led the Council to award the Makdougall Bris- 
bane prize to Mr Lister, and I hope I have in some measure 
succeeded. I cannot express the satisfaction we all feel in having 
a paper so eminently worthy of the award. 
