DEGERMING EFFICIENCY OF HEXACHLOROPHENE SOAPS 287 is of sufficient value relative to the other two coefficients to warrant its being observed and calculated, and used in the general over-all inter- pretation of all of the data. Calculated also from the above curves (Chart 2), it becomes: c//1 = 100,000/4,250,000 = 0.02 Coefficient = 100 -- (C/,'t)) 100 = 98% It will soon become evident to anyone using this test procedure, or any other modification of this mul- tiple-basin technique for determining the bacterial removal from the skin, that exact duplicate results are difficult to o•ain. Due to the individu3.1 differences in the subjects themselves, both as to normal skin flora and as to uniformity of tech- nique applied, some will find their original counts to be much higher than shown here, while others will be found to be appreciably lower. These may range all the way from around 12,000,000 down to around 1,000,000. Thus, .4 of curve may be found to be any figure be- tween these two extremes, instead of 4,250,000 as the above chart shows it to be for these average test data. The point B of the same curve may likewise rise or fall above or below where it is found to be as pre- sented in the above chart (at 2,400,000). Experience has indicated, how- ever, that no matter where the original or control counts may be, the respective percentage reductions (or coefficients as calculated above) remain quite constant. Thus, when using hexachlorophene (2 per cent on soap-weight basis) as the degerming agent, be the initial count 10,000,000 or 2,000,000, for example, the D/.4 equivalent of over-all reduction coefficient will generally fall within the range of 95 4- 5 per cent. In a few cases, it may go as low as 85 per cent, or even once in a while to 80 per cent, due to the personal factors referred to above. With a series of subjects, the majority should defi- nitely show results in the 95 per cent ra, nge. Similarly, the results for the resident coefficient may vary for the same reasons. The slope of the curve .4B (or its equivalent) may become steeper in some cases or less steep in other tests. Thus, the results for D/B may safely vary through a range. In gen- eral, this range for the coefficient is also 95-+5 per cent, but occa- sionally may go as low as 80 per cent, for the same reasons as given above. Thus, for example, if the original control should be found to be .4'B' instead of .4B, with the degerming effect shown by CD as before, the respective coefficients would then be: 1. D/,-'I': 50,000/1,600,000 = 0.03 coeff. = 100 - 3 = 97% 2. D/B': 50,000/900,000 = 0.05 eoeff. --- 100 -- 5 = 95% 3. C/•I': 100,000/1,600,000 -- 0.06 coeff. = 100 -- 6 = 94% And, if the original control was found to be XY instead of and the degerm curve CD then the respective coefficients would become: 1. D/X: 50,000/3,100,000 = 0.02 coeff. = 100 -- 2 = 98%

288 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 2. D/Y: 50,000/1,750,000 = 0.03 coeff. = 100 -- 3 = 97% 3. C/X: 100,000/3,100,000 = 0.03 coeff. = 100 -- 3 = 97% Calculating in the same manner, using the same three representa- tions as being within the range variations for the controls (namely, AB, XY, or A'B') but having the degerming data represented by the "high" rather than the "low" curves (i.e., C'D' instead of CD), which results are practically possible, we find: skin equal to or preferably better than that as produced by the normal surgical scrub-up procedure. Therefore, we set as our criterion for satisfactory degerming action an end point which indicates that this desired action has been accom- plished by, at least, the fifth wash- ing preferably by the third. See lines in Chart 2 which run from Basin 3 perpendicular to the ab- scissa and from Basin 10, "af•ter alcohol wash" count, parallel to Control Degerm Curve Curve ,--Coefficient or Percentage Reduction--, 1. 2. 3. Transient- Over-all Resident Resident AB C'D' 90 80 80 XY C'D' 84 70 67 A'B' C'D' 67 50 40 Actually, if the control was found to be in the range of either Curve A'B' or C'D', then the degerm curve would be found to be lower than C'D', and perhaps even lower than CD. This explains why these coefficients are low for the last two sets just tabulated, and also shows, should one obtain such data, that the material is poor as a de- germing agent and if it is a hexachlorophene mixture being tested either the subjects are not satisfactory or the mixture has been compounded improperly, or has too little hexachlorophene in it. We assume in this connection that the basic criterion for a satis- factory degerming agent is that it should, when used according to this procedure, show a lowering in count of bacteria removed from the the abscissa. Where these two lines meet is the "ideal" or critical point. A good degerming material should show its third basin reading to be below that point. Naturally, should the control itself be at or near that point, another subject should be used for the testing. The surgical scrub-up curve, which shows how the count of the skin bacteria removed by ordinary soap decreases with successive wash- ings, carried out in exactly the same manner for nine consecutive basins, or washings, followed by a dip into 70 per cent alcohol, and then washing again in order to collect the tenth basin data. This procedure is not exactly as carried out in a normal hospital scrub-up, but it is aksumed here, and by others doing similar testing, that