ANTISEPTICS 167 



far as is known, the activity of these agents is limited to the 

 killing of bacteria outside the animal body, but still even this is 

 of high importance; in the body the scope of the use of 

 antiseptics is, amongst other factors, determined by all of them 

 being general protoplasmic poisons. 



Methods. — These vary very much. In early inquiries the amount of 

 an antiseptic necessary to prevent putrefaction in, e.g., bouillon, urine, 

 etc., was studied ; but as bacteria vary in their powers of resistance, the 

 method was unsatisfactory, and now an antiseptic is usually judged of by 

 its effects on pure cultures of definite pathogenic microbes, and in the case 

 of a sporing bacterium, the effect on both the vegetative and spore forms 

 is investigated. The organisms most used are the staphylococcus 

 pyogenes, streptococcus pyogenes, and the organisms of typhoid, cholera, 

 diphtheria, and anthrax — the latter being most used for testing the action 

 on spores. The best method to employ is to take sloped agar cultures 

 of the test organism, scrape off the growth, and mix it up with a 

 small amount of distilled water, filter this emulsion through a plug of 

 sterile glass wool held in a small sterile glass funnel, add a measured 

 quantity of this fluid to a given quantity of a solution of the antiseptic in 

 distilled water, then after the lapse of the period of observation to remove 

 one or two loopfuls of the mixture and place them in a great excess of 

 culture medium ; here it is preferable to use fluid agar, which is then 

 plated and incubated. In dealing with strong solutions of chemical 

 agents it is necessary to be sure that the culture fluid is in great excess, 

 so that the small amount of the antiseptic which is transferred with the 

 bacteria may be diluted far beyond the strength at which it still can have 

 any noxious influence. Sometimes it is possible at the end of the period 

 of observation to change the antiseptic into inert bodies by the addition 

 of some other substance, and if the inert substances are fluid there is no 

 objection to this proceeding ; but if in the process a precipitate results, 

 the bacteria may be carried down with the precipitate and may escape 

 the culture test. To test the effects of antiseptics on spores Koch soaked 

 silk threads in an emulsion of anthrax spores and dried them. These 

 were then subjected to the action of the antiseptic, well washed in water, 

 and laid on the surface of agar. In using this method to test the 

 efficiency of mercuric chloride it was found necessary to break up the 

 metallic salt with ammonium sulphide to prevent the formation on the 

 spore case of an albuminate which protected the contents from the anti- 

 septic action. Such an occurrence only takes place with spores, and the 

 method given above, in which the small amount of antiseptic adhering 

 to the bacteria is swamped in an excess of culture fluid, can safely be 

 followed, especially when a series of antiseptics is being compared. 

 Krbnig and Paul introduced what is known as the garnet method for 

 testing antiseptics. In this, small garnets of equal size are carefully 

 cleaned, dipped in an emulsion of anthrax spores, and allowed to dry. 

 They are then placed in mercuric chloride, and from time to time some 

 are removed, gently washed, and treated with ammonium sulphide to 

 decompose the chloride. They are then well shaken in a measured 

 quantity of water. This is plated, . and the number of anthrax colonies 

 devoloping is counted. 



Much attention has been paid to the standardisation of antiseptics, 

 and a watery solution of carbolic acid is now generally taken as the 



