ANTISEPTICS 167 



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, and 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 ; such a procedure is preferable 

 to the use of bouillon tubes, as any colonies developing can easily be 

 recognised as belonging to the species of bacterium used. 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 then test the condition of the bacteria, and if the inert 

 substances are fluid there is no objection to this proceeding ; but if in 

 the process a precipitate results, then it is better not to have recourse 

 to such a method, as sometimes the bacteria are carried down with the 

 precipitate and may escape the culture test. The advisability of, when 

 possible, thus chemically changing the antiseptic was first brought to 

 notice by the criticism of Koch's statements as to the efficacy of 

 mercuric chloride in killing the spores of the b. anthracis. The method 

 he employed in his experiments was to soak silk threads in an emulsion 

 of anthrax spores and dry them. These were then subjected to the 

 action of the antiseptic, well washed in water, and laid on the surface of 

 agar. It was found, however, that, with threads exposed to a far higher 

 concentration of the corrosive sublimate than Koch had stated was 

 sufficient to prevent growth, if the salt were broken up by the action of 

 ammonium sulphide and this washed off, growth of anthrax still occurred 

 when the threads were laid on agar. The. explanation given was that 

 the antiseptic had formed an albuminate with the case of each spore, and 

 that this prevented the antiseptic from acting upon the contained 

 protoplasm. 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. 

 Kro'nig 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 

 developing is counted. 



Ponder and Woodhead have introduced an ingenious apparatus by 

 which the effects of different concentrations of an antiseptic on the 

 vitality of such an organism as the b. coli can be automatically 

 recorded. 



Much attention has been paid to the standardisation of antiseptics, 

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

 standard with which other antiseptics are compared. Rideal and 

 Walker point out that 110 parts by weight of B.P. carbolic acid equal 



