44 RELATIVE ACTIVITY OF VARIOUS ANTISEPTICS 



saturated solution. A temperature over 125 Fahr. weakens 

 or destroys the enzymes. 



Drugs act differently on different ferments. While 

 l-52,000th part of corrosive sublimate, as already indicated, 

 arrests the action of ptyalin, 1 part in 720 is needful to 

 arrest the action of rennet, which is, however, destroyed by 

 1- 1000th part of borax, 1 part of which in 100 is required to 

 destroy ptyalin. For destruction of rennet, bromine and 

 chlorinated lime are specially effective. Creosote, although 

 it has small effect on the enzymes, in solution of 1 part to 500 

 destroys yeast cells, and, in solution of half that strength, 

 kills bacteria. The mould fungi are destroyed by the same 

 agents which kill yeast and bacteria. 



Bacteria of different sorts exhibit some differences in 

 their susceptibility to different antiseptics ; indeed, the 

 susceptibility somewhat varies in the same bacteria when 

 raised in different media. It is more easy to prevent than 

 to arrest development of bacteria. As already pointed out, 

 the spores have much greater resisting powers than the 

 fully-developed bacteria. The fully-developed bacteria are 

 destroyed by exposure for an hour to a temperature of 150 

 to 168 Fahr., but the spores require more prolonged ex- 

 posure at 212 Fahr. Moist heat, having a greater power of 

 softening and penetrating the spore envelope, is more 

 effectual than dry heat. Milk containing the bacillus of 

 tubercle or other specific disorder may be rendered inno- 

 cuous by five minutes' boiling. 



Experiments bearing on the power of different substances 

 to prevent the development of bacteria in various stages 

 and solutions, to kill them, or to arrest development and 

 reproduction of their spores, have been carried out by many 

 good observers. The plan of procedure has generally been 

 to add to carefully prepared sterilised fluids in test tubes, 

 known quantities of the disinfectant to be tested, and then 

 introduce a drop of liquid containing bacteria or their spores, 

 Such experiments show that the agents which most promptly 

 and effectually arrest the action of enzymes also prove the 

 most destructive to bacteria. Of corrosive sublimate, 

 l-5805th part kills the developed parasite ; 1-25, 258th 

 part prevents the development of bacteria taken from 



