ANTISEPTICS AND DISINFECTANTS. 157 



chlorine in a closed vessel. After a time they were 

 transferred to a nutrient medium to test their vitality. 

 To test the power of sulphurous acid gas, the spores 

 were spread about in a room in which the gas was 

 generated by burning sulphur in the ordinary way 

 for disinfecting a room. To test chemicals which 

 might be recommended for disinfecting vans and 

 railway carriages, spores were laid on boards which 

 were then washed or sprayed, and the spores then 

 transferred to the nutrient gelatine. 



By such simple methods Koch investigated a 

 long list of chemical reagents, and according to 

 these experiments the salts of mercury, and the 

 chloride especially, proved most valuable. Where 

 heat is not admissible, these compounds were 

 therefore highly recommended, though their poi- 

 sonous nature is a drawback to their indiscrimi- 

 nate use. Koch states, for disinfecting a ship's 

 bilge, where a 5 per cent, solution of carbolic 

 acid must be left for forty-eight hours, a i in 1000 

 solution of mercuric chloride would only require a 

 few minutes. 



There is, on the other hand, reason for doubting 

 the efficacy of mercuric chloride ; for, though 

 anthrax spores subjected to a i in 20,000 solution 

 of mercuric chloride for ten minutes, and then 

 washed in alcohol, gave no growth in nutrient 

 gelatine, silk threads exposed for ten minutes to 

 a i in 20,000 solution, or even i in 10,000, still 

 proved fatal to mice. 



