ON THE ANTISEPTIC PRINCIPLES 275 



covered with a plate of clean metal, such as block tin, fitting 

 its surface pretty accurately, and overlapping the surrounding 

 skin an inch or so in every direction and retained in position 

 by adhesive plaster and a bandage, it will be found, on removing 

 it after twenty-four or forty-eight hours, that little or nothing 

 that can be called pus is present, merely a little transparent 

 fluid, while at the same time there is an entire absence of the 

 unpleasant odour invariably perceived when water dressing 

 is changed. Here the clean metallic surface presents no 

 recesses like those of porous lint for the septic germs to 

 develope in, the fluid exuding from the surface of the granu- 

 lations has flowed away undecomposed, and the result is the 

 absence of suppuration. This simple experiment illustrates 

 the important fact that granulations have no inherent ten- 

 dency to form pus, but do so only when subjected to preter- 

 natural stimulus. Further, it shows that the mere contact 

 of a foreign body does not of itself stimulate granulations 

 to suppurate; whereas the presence of decomposing organic 

 matter does. These truths are even more strikingly exempli- 

 fied by the fact that I have elsewhere recorded (Lancet, 

 March 23rd, 1867), that a piece of dead bone free from 

 decomposition may not only fail to induce the granulations 

 around it to suppurate, but may actually be absorbed by 

 them ; whereas a bit of dead bone soaked with putrid pus in- 

 fallibly induces suppuration in its vicinity. 



Another instructive experiment is, to dress a granulating 

 sore with some of the putty above described, overlapping the 

 sound skin extensively; when we find, in the course of 

 twenty-four hours, that pus has been produced by the sore, 

 although the application has been perfectly antiseptic; and, 

 indeed, the larger the amount of carbolic acid in the paste, 

 the greater is the quantity of pus formed, provided we avoid 

 such a proportion as would act as a caustic. The carbolic 

 acid, though it prevents decomposition, induces suppuration 

 obviously by acting as a chemical stimulus; and we may 

 safely infer that putrescent organic materials (which we 

 know to be chemically acrid) operate in the same way. 



In so far, then, carbolic acid and decomposing substances 

 are alike; viz., that they induce suppuration by chemical 

 stimulation, as distinguished from what may be termed simple 



