AN ADDRESS OX A NEW ANTISEPTIC DRESSING 321 



development. The test applied was, of course, an extremely severe one. In 

 actual surgical practice the discharge which pours into the dressing is pure to 

 begin with, supposing the wound to be aseptic at the outset. The septic agency 

 only acts from without where the dressing has not been washed by the discharge, 

 and in a far milder form than here, where a potent septic drop was used. Thus 

 we had clear evidence that the cyanide of zinc really is an antiseptic. On the 

 other hand, it turned out to be not so powerful antiseptically as our double 

 cyanide so called. In order to compare the two salts I made another experiment 

 similar to that last described. I packed three pieces of glass tube with gauze 

 in two inches of their length, one of the gauzes being charged with cyanide of 

 zinc and another with the so-called double cyanide (neither of these gauzes 

 having been treated with solution of bichloride of mercury), while the third 

 gauze was unprepared. Serum of horse's blood was poured into the upper end 

 of each vertically held tube till it thoroughly soaked the mass of gauze, after 

 which each gauze was inoculated septically at the centre of its upper end. The 

 tubes were then placed vertically in stoppered bottles in the incubator. It 

 happened that in the septic liquid used for the inoculation that I used there 

 was, among other organisms, a species of streptococcus which had a remarkable 

 power of producing an acid fermentation in blood-serum. After four davs 

 I proceeded to examine the contents of the three tubes. In the unprepared 

 gauze there was utter putrefaction. In the gauze prepared with cyanide of 

 zinc only, no putrefaction had taken place, but acid fermentation had occurred : 

 both at the upper and lower end of the gauze litmus paper was reddened on 

 application to the serum. In the putrid gauze turmeric paper was most 

 intensely reddened, much more so than by normal blood-serum, an alkaline 

 fermentation having occurred there. On the other hand, with the gauze that 

 contained the double cyanide, with mercury as well as zinc, both at the upper 

 and lower end the turmeric paper was reddened exactly as it was by the normal 

 blood-serum. This state of things continued the next day ; but on the following 

 day, six days after the commencement of the experiment, I found that at the 

 upper end, in the vicinity of the inoculated spot, this double-cyanide gauze 

 purpled litmus, while at the lower end it still reddened turmeric. At the end 

 of seven days the same condition persisted. After eight da\s. ho\\o\er. both 

 the upper and lower end of the gauze purpled litmus. This ]xxniliar septic 

 organism, with the power of producing acid fermentation in serum, had gradually 

 worked its way, in spite even of the cyanide of zinc and mercury : but tlie 

 cyanide of zinc and mercury, you observe, had been much more efhcacious 

 than the cyanide of zinc alone. The cvanide of zinc had jirevented the 

 development of organisms that j^roduced putrefaction, and only permitted the 



