COMPARATIVE EFFICACY OF DISINFECTANTS 83 



prevent putrefaction do not kill the bacteria, they only arrest growth and 

 multiplication. 



II. LETHAL VALUE FOR SPOKELESS TUBERCLE BACILLI. 



Inferior lethal coefficient ; the time is given in which tubercle bacilli 

 (from cultures, not in sputum) are killed. From Yersin (54). 



Carbolic acid 5% 30 seconds 



,, l% I minute 



Absolute alcohol 5 minutes 



lodoform i% 5 



Ether 10 



Corrosive sublimate . . . 0-1% 10 ,, 



Thymol '3% 3 hours 



Salicylic acid 0-25% 6 



To kill the bacteria in sputum, where they are embedded in mucus, 

 a much longer time is necessary, e. g. 10 per cent, lysol for twelve hours. 

 The figures in the table were obtained by mixing tubercle bacilli from 

 a growing culture with the fluids, taking out samples from time to time, 

 and sowing them on culture media. The values given may be regarded 

 as being good for most sporeless bacteria, the sensitiveness of which is 

 illustrated by this example. 



III. LETHAL VALUE FOR ANTHRAX SPORES. 

 From Paid u. Krb'nig (55). 



Substance. Concentration. Time (Temperature 18 C.)- 



Corrosive sublimate . 1-7 % ( 1 6 litres) 12-14 minutes 



0-84% ( 32 ) 24-30 



'42% (64 ) 45-60 



... 0-2 % (128 ) 60-80 



... o-i % (256 



Nitrate of silver . . 4-25% ( 4 



. . 0-08% (200 



Sulphate of copper . . 16- % ( I 



Sugar of lead . . . 3 2 '5 % ( * 



Sulphuric acid . . 4-9 % ( 2 



Caustic potash . . 5-6 % ( i 



Permanganate of potash . 3-95% ( 4 



Bichromate of potash . 7-4 % ( 4 



) more than 120 minutes 



) 15-16 minutes 



) not in loj hours 



) not in io days 



) not in 7 



) not in 30 hours 



) 1 8 hours 



) 40 minutes 



) not in 4 days 



Permang. of potash, 8 litres, plus 8 litres HC1 5 minutes 



Chlorine water . . 0-22% ( 32 litres) 2 



Bromine water . . 0-5 % ( 32 ) 2 



Carbolic acid . . 5 % ... not in 24 hours 



Formaldehyde . . 5 % ... 120 minutes 



The lethal concentration for spores is determined in the following way. 

 A suspension of the spores in water is dried upon silk threads, pieces of 

 glass, or, better still, upon carefully-cleaned garnets, which are then laid in 

 the disinfectant. Specimens are taken out at intervals and sowed in nutri- 



G 2, 



