434 



SCIENCE. 



[Vol. II., No. 34. 



ments go, are not shown to have any germicide vaKie ; 

 viz., — 



Per cent. 

 Fowler's solntion failed in the proportion of ... 40 

 Sodium hyposulphite failed in the proportion of . . . 32 

 Sodium sulphite, exsiccata, failed in the proportion of . 10 

 Ferric sulphate (saturated solution) failed in the propor- 



tion of 



Potassium iodide failed in the proportion of . . . S 

 Liq. zinci chloridi failed in the proportion of . . . S 

 Boracic acid (saturated solution) failed in the proportion of 4 

 Zinc sulphate failed in the proportion of .... 20 

 Sodium horate (saturated solution) failed in the propor- 

 tion of . . .■ 4 



Sodium salicylate failed in the proportion of . . . 4 



Having ascertained the germicide vahie of certain 

 reagents for a single micro-organism, the question 

 xirises as to whether we are justified in assuming that 

 other organisms of the same class, and especially 

 pathogenic bacteria, will be destroyed by the same 

 reagents in lilce proportion, or, in other words, wheth- 

 er we can generalize from the data obtained. It is 

 ■evident, that, if eacli of the reagents named gives iden- 

 tical results with several distinct species of bacteria, 

 we shall be justified in assuming that the value ob- 

 tained will be constant for ofher organisms, known 

 or unknown, of the same class ; whereas, if marked 

 differences are found as to the vital resistance of 

 different bacterial organisms to these reagents, no 

 generalization will be possible, and the value for 

 each distinct organism of the class can only be fixed 

 by experiment. To solve this question, experiments 

 have been made as follows : — 



a. Upon the micrococcus of pus. 



b. Upon the micrococcus of septicaemia in the rab- 

 bit. 



c. Upon bacterium termo, in its active motile stage, 

 as found in afresh culture. 



d. Upon the bacteria in broken-down beef-tea which 

 had been freely exposed to the air, and in which all 

 active development had ceased. 



The results sliow, that, in general, those reagents 

 which destroyed the vitality of the micrococcus from 

 pus are destructive to organisms of the same class, 

 and that tlieir relative value as germicides is not 

 changed when a diilerent micro-organism is used as 

 the test of this value. Moreover, the reagents which 

 were found to be practically valueless as germicides 

 in the first series of experiments — e.g., ferric sul- 

 phate, sodium sulphite, and liyposulphite, boracic 

 acid, etc. — proved to be equally without value when 

 the test was extended to other micro-organisms of 

 the same class. But the reagents found to possess 

 decided germicide power have, in some cases, a dif- 

 ferent value for different organisms: in other words, 

 the vital resistance of different bacterial organisms to 

 the reagents in question is not in all cases the same. 



Tlius, sulphuric acid failed to destroy B. termo and 

 the micrococcus from pus in the proportion of 0.25 %; 

 but one-fourth of tliis amount (0.06 %) destroyed 

 the vitality of the sej)tic micrococcus. 



Caustic potash destroyed the septic micrococcus in 

 the proportion of 2 %, but failed to kill the micrococ- 

 cus of pus in four times this amount (8 %). The 

 value, as a germicide, of the solution of ferric sul- 



phate and sulphuric acid in water, which has been 

 extensively recommended by sanitarians as a disin- 

 fectant, evidently depends upon the sulphuric acid 

 which the solution contains. To insure the destruc- 

 tion of all bacterial organisms and of the reproduc- 

 tive spores of tliose species which multiply by spores- 

 as well as by transverse fission, such a solution sliould 

 be used in suificient quantity to subject tlie material 

 to be disinfected to the action of the acid in the pro- 

 portion of at least five per cent for a period of two- 

 hours. 



The quantity of carbolic acid used to accomplish 

 the same result should not be less than five per 

 cent, for it is necessary to keep on the safe side; and 

 we do not know, at present, whether all of the path- 

 ogenic bacteria, hypothetical or demonstrated, form 

 spores or otherwise. In the case of the antlirax ba- 

 cillus and of Kocli's bacillus of tuberculosis, tliis has 

 been proved to be true ; and we have ample experi- 

 mental evidence to show that these reproductive 

 bodies possess very great resistance to heat and to- 

 those chemical reagents whicli destroy bacterial or- 

 ganisms in their ordinary condition of rapid growth 

 and multiplication by fission. 



Evidently, therapeutic value — assuming the cor- 

 rectness of the germ-theory — cannot be gauged by 

 germicide power alone, for it is possible that a re- 

 agent which possesses this power in but sliglit degree, 

 or not at all, may nevertheless be capable of restrict- 

 ing the development of pathogenic organisms, and 

 thus limiting tlieir povrer for mischief. 



The following table shows the percentage required 

 to destroy vitality, and also that required to prevent 

 the development of the micrococcus of pus : — 



An inspection of the table shows that the potent 

 germicides in our list restrict multiplication in quan- 

 tities considerably less than are required to destroy 

 vitality. In the case of iodine tl],e difference is- 

 eightfold ; in that of carbolic acid, fourfold ; in that 

 of sulphuric acid, twofold, etc. 



We also see that the agents at the bottom of the- 

 list, — ferric sulphate, boracic acid, and sodium bibo- 

 rate, — in the proportion of five-tenths per cent, pre- 

 vent the multiplication of bacterial organisms, and are- 

 consequently antiseptic agents of value, although ia 

 saturated solution they fail to kill these organisms. 



In the case of ferric sulphate, and also of zinc sul- 

 phate and zinc chloride, tliis power to prevent the 

 development of micro-organisms seems to be due to 



