THE VITAL PHENOMENA OF BACTERIA. 73 



death of the spores inside of 24 hours. A .2% 

 solution of corrosive sublimate caused death of 

 the spores inside one hour, as was also the case 

 with a .2% solution of fresh chlorine water, while 

 other agents required many days ; a 5% carbolic 

 acid solution for instance needed more than 

 forty days. On' the other hand, many sub- 

 stances caused death of the vegetative forms 

 in the course of a few minutes. 



A better understanding of these processes 

 was arrived at when it became recognized that 

 mechanical purification must precede disinfec- 

 tion. Acids and alkalies again came into re- 

 pute, and it was found that strongly concen- 

 trated preparations of the alkalies, of caustic 

 soda, of quick-lime, and of milk ' of lime dis- 

 solved in water (CaO+H 2 O=Ca (OH) 2 ) were 

 good disinfectants, and indeed that common 

 soda itself killed germs ; that a direct influence 

 was exerted upon the proteid of the bacterial 

 cell was consequently inferred. For the same 

 reason the acids act as disinfecting agents. 

 Bacteria are more susceptible to the action of 

 the mineral acids, like sulphuric, nitric and hy- 

 drochloric acids, than to that of the vegetable 

 acids like tartaric and citric, and least suscep- 

 tible toward those which some bacteria them- 

 selves produce, such as acetic, butyric and 

 lactic. When the latter are formed in the 



