BUREAU OF ANIMAL INDUSTRY. 609 



Eor cent. (1 : 1000000) it was found that with both solutions tubes inoculated with the 

 acterium after a exposvure of 2 and 5 minutes were opalescent, the bacterium in- 

 troduced liaving multiplied, while the remaining tubes (10 to 30 minutes) were ster- 

 ile. Tliese two solutions, therefore, were stdl powerful enough to kill the germ in 

 10 minutes. The dilution had been carried so far as to make them practically equiv- 

 alejit in disinfectant power. 



Sulphate of copper. — This disinfectant, which seems to be more effective than 

 most other metallic salts, was tried in solutions containing 2 per cent., J per cent., 

 iV per cent. Both the 2 per cent, and i per cent, solutions destroyed the germ within 

 5 minutes. Tubes inoculated with the bacterium after an exposm-e to the tV per 

 cent, solution for 5, 10, and 15 mmutes became turbid; those inoculated after an 

 exposure of 20, 25, and 30 minutes remained clear. 



The disiii.fectant power for short periods of time may be said to lie between J and 

 -i\y per cent. In this, as in other tests, one or two drops of the culture were added 

 to 5" of the disinfectant. A slight flocculent precipitate formed each time. 



Of JiijdrocJiloric acid a .2 per cent, solution of the acid, made by adding 4.2" of 

 chemically pure acid (containing about 40 per cent. HCl) to 95.8" of water, de- 

 stro3-ed tlie germ in less than 5 minutes. 



Chloride of zinc. — A 10 per cent, solution of this salt faUed to destroy the vitaHty 

 of the bacterium in 10 minutes; 20" of Squibbs' chloride of zinc, containing 50 per 

 cent, of the salt, were added to 80" of sterile distilled water to make a 10 per cent, 

 solution. A drop from a cultaire five days old was mixed with 5" of tliis solution, 

 from which mixture tubes were inoculated at the end of 5, 10, 15, 25, and 30 min- 

 utes. The two first tubes became clouded. 



Sulphuric acid. — A .05 per cent, solution (1: 2000) was fatal to the bacterium of 

 ho<r-cholera in less than 10 mmutes. 



Without going into detail, it is sufficient to say that the results were reached as 

 indicated above. Tubes containing sterile beef broth were inoculated at the end of 

 5, 10, 15, 20, 25, and 30 minutes with bacteria exposed to i per cent, and i per cent. 

 No development. Those inoculated with -4V per cent, became clouded, each being a 

 pure culture of the bacterium inoculated. When /^^ per cent, was tried, only the 

 5-ininute tube became clouded. The solution (by weight) was made from sulphuric 

 acid containing 96 per cent, of the acid (specific gravity 1.838). 



It must be remembered that the foregoing tests were made upon 

 bacteria in an active vegetative state. It is probable that in the dried 

 condition it would have taken solutions of the same strength some- 

 what longer time to destroy their vitality. To briefly summarize the 

 results, placing the least eifective substance first, we obtain the fol- 

 lowing table: 



Chloride of zinc in a 10 per cent, solution destroyed the bacterium in liquid cultures 

 in 10 to 15 minutes. 



Carbolic acid, 1 to H per cent. (1 : 100), in 5 minutes. 



Iodine water in 15 minutes. 



Hydrochloric acid, i per cent. (1 : 500), in less than 5 minutes. (Only a .3 per cent, 

 solution of this acid tried.) 



Sulphate of copper. -^ per cent. (1 : 1000), in 15 to 20 minutes. 



Sulphuric acid, ^Vr per cent. (1 : 2000), in less than 10 minutes. 



Permanganate of potash, x^ per cent. (1 : 5000), in 15 minutes. 



Mercuric chloride, rh per cent. (1 : 75000), less than 5 minutes. 



Mercuric iodide in Tn^^jij per cent. (1 : 1000000), in 10 minutes. 



The above table w.ould no doubt be somewhat changed bv mixing 

 %drus imbedded in large quantities of organic matter with the disin- 

 fectant solutions. It gives, however, a good working basis for ex- 

 periments on a large scale, and it throws out at once the use of chlo- 

 ride of zinc and perhaps carbolic acid. 



In order to determine how much stronger solutions than those 

 above given would be required to destroy the dried bacteria, the fol- 

 lowing experiment was carried out : 



Spleen pulp containing large numbers of bacteria was rubbed on sterile cover- 

 glasses so as to make a thm film, and allowed to dry for 2 davs under a plugged 

 funnel. A solution of mercuric chloride, 1 : 50000, was poured upon the cover- 

 glasses, and one was removed after 1^, 2, 3, 5, 7, 10, 15, 17, and 20 minutes, washed 

 in about 100" of sterile water, and dropped into tubes containing beef infusion. 

 39 AG— '86. 



