12 REPORT—1896. 
dressing capable of preventing the access of other living organisms till 
the time should have arrived for changing it. 
Carbolic acid lent itself well to both these objects. Our experience 
with this agent brought out what was, I believe, a new principle in 
pharmacology—namely, that the energy of action of any substance upon 
the human tissues depends not only upon the proportion in which it is 
contained in the material used as a vehicle for its administration, but also 
upon the degree of tenacity with which it is held by its solvent. Water 
dissolves carbolic acid sparingly and holds it extremely lightly, leaving it 
free to act energetically on other things for which it has greater affinity, 
while various organic substances absorb it greedily and hold it tenaciously. 
Hence its watery solution seemed admirably suited for a detergent lotion 
to be used for destroying any microbes that might fall upon the wound 
during the operation, and for purifying the surrounding skin and also the 
surgeon’s hands and instruments. For the last-named purpose it had the 
further advantage that it did not act on steel. 
For an external dressing the watery solution was not adapted, as it 
soon lost the acid it contained, and was irritating while it lasted. For 
this purpose some organic substances were found to answer well. Large 
proportions of the acid could be blended with them in so bland a form as 
to be unirritating ; and such mixtures, while perpetually giving off 
enough of the volatile salt to prevent organic development in the dis- 
charges that flowed past them, served as a reliable store of the antiseptic 
for days together. 
The appliances which I first used for carrying out the antiseptic prin- 
ciple were both rude and needlessly complicated. The years that have 
since passed have witnessed great improvements in both respects. Of 
the various materials which have been employed by myself and others, 
and their modes of application, I need say nothing except to express my 
belief, as a matter of long experience, that carbolic acid, by virtue of its 
powerful affinity for the epidermis and oily matters associated with it, 
and also its great penetrating power, is still the best agent at our dis- 
posal for purifying the skin around the wound. But I must say a 
few words regarding a most important simplification of our procedure. 
Pasteur, as we have seen, had shown that the air of every inhabited 
room teems with microbes ; and for a long time I employed various more 
or less elaborate precautions against the living atmospheric dust, not 
doubting that, as all wounds except the few which healed completely by 
the first intention, underwent putrefactive fermentation, the blood must 
be a peculiarly favourable soil for the growth of putrefactive microbes. 
But I afterwards learnt that such was by no means the case. I had 
performed many experiments in confirmation of Pasteur’s germ theory, 
not indeed in order to satisfy myself of its truth, but in the hope of 
convincing others. I had observed that uncontaminated milk, which 
would remain unaltered for an indefinite time if protected from dust, 
