8 WOUND TEEATMENT 



The question now arises, "How are we to know 

 the real value of a germicide ? " In the last few years, 

 both in this country and in Europe, there have been 

 rapid advancements made in the accurate standard- 

 ization of disinfectants. It is time that the old state- 

 ments in textbooks that bichlorid of mercury kills 

 anthrax in so many hours, and Strep+ococcu^ pyogenes 

 in so many minutes, should be discarded. The results 

 depend entirely on the strains of the organisms tested 

 and the method used. 



One strain of Streptococcus pyogenes may be killed 

 in five minutes while another, by the same method, 

 will require twice the time. 



Carbolic acid and the salts of the heavy metals, such 

 as silver, copper, and mercury, have been mostly used 

 as disinfectants. There is now a tendency to discard 

 these for the more easily applied preparations, as their 

 general fault lies in their lack' of efficiency in the pres- 

 ence of organic matter^that is, blood and pus. 



Another group of disinfectants not used to any ap- 

 preciable extent but possessiiig high efficiency, is the 

 essential oils. They owe their germicidal value to 

 their phenol content, which, in some instances, is very 

 high. Thymol, for example, which is a phenol obtained 

 from the oil of thyme, is twenty-five times more pow- 

 erful than carbolic acid. It is unfortunate that the 

 expense of these oils and the inconvenience of apply- 

 ing them have limited their use, for they are only 

 slightly toxic, do not coagulate organic matter to any 

 appreciable extent, and are only slightly irritating. 



The germicidal value of most of the commercial 

 coal-tar disinfectants is due to the cresols — paracresol, 

 metacresol, and orthocresol — ^whieh are variable in their 

 germicidal efficiency. 



