KOCH'S EXPERIMENTS 45 



meat infusions ; but it requires a strength of 1 in 2525 

 to prevent reproduction of spores in unboiled meat infusion, 

 and still, stronger solutions to penetrate and kill the spores. 

 Chlorine, chlorinated lime, bromine, iodine, and quinine 

 stand next in activity. Sodium sulphite is about l-10th the 

 strength of quinine. Compared with corrosive sublimate, 

 it requires twenty times the amount of thymol, salicylic 

 acid, or potassium permanganate to prevent development 

 of bacteria, and sixty times the amount to prevent repro- 

 duction of spores. Sodium hyposulphite has very little 

 action. Carbolic acid did not stand so high as expected. 

 The fresh blood of an animal just dead from anthrax 

 must be mixed with its own bulk of a 1 per cent, solution 

 in order to destroy the bacilli, and enable it, without harm, 

 to be injected into another animal. A half per cent, solution 

 fails to destroy the bacilli. 



Koch's experiments with anthrax spores constitute re- 

 liable tests of the value of disinfectants. Solutions of the 

 several substances, of specified strength, were placed in 

 tubes, their mouths stopped, as is generally done, by cotton 

 wool ; and threads steeped in fluids containing bacilli and 

 their spores were carefuUy introduced. Some of these 

 threads were removed from day to day, and subjected to 

 microscopic examination. Even after one hundred days' 

 exposure to the antiseptic, some threads still exhibited 

 bacilli. Chlorine water, freshly made, bromine 2 per cent, 

 solution, iodine 1 part in 7000, corrosive sublimate 1 per 

 cent, in water, were found effectually to destroy these 

 anthrax spores with which they had been in contact one 

 day. Formic acid, specific gravity 1120, destroyed all 

 spores after four days' exposure. In five days all spores 

 were killed by 5 per cent, watery solutions of chlorinated 

 lime and ferric chloride. One per cent, of arsenic in water, 

 and the same proportion of quinine in acidulated watery 

 solution, were effective in ten days. Oil of turpentine took 

 five days, ether thirty days. The results with carbolic acid 

 were disappointing ; a 1 per cent, solution had not much 

 effect on the spores, even when exposure was prolonged for 

 fifteen days ; and a five per cent, solution was required to 

 secure their destruction in one day. Like salicylic, boric, 



