100 Comparative Power of some Disinfectants. 



bottles must have been exposed to a temperature nearly, if 

 not quite, up to 212° Fahr. 



(1.) One piece each for 10 and 30 minutes. The solution 

 in both remained transparent, but I was somewhat doubtful 

 of the trustworthiness of the result, as that which con- 

 tained the unheated paper showed only a slight cloudiness 

 after 4 days. This circumstance will be referred to again. 



(2.) One piece each for 15 and 45 minutes. The solution 

 with the 15 minutes piece became cloudy only in 4 days, the 

 test bottle being opalescent at the end of 2J days. The 45 

 minutes piece had no effect. 



(3.) One piece each 15 and 25 minutes. Solution in both 

 cases remained transparent after 12 days. 



The conclusion come to, therefore, is that an exposure of 

 these microzymes to a temperature of about 212° Fahr. must 

 be continued for at least 15 or 20 minutes to ensure their 

 destruction. 



Two circumstances of considerable interest came out in the 

 course of the investigation, which I have reserved for separate 

 notice. The first was that when the bacterialised paper had 

 been kept for between two and three months, the organisms 

 seemed to have lost their power of reproduction. What the 

 cause may have been I am not prepared to say, but that this 

 happened was certain, and it caused a good deal of confusion 

 and perplexity in my mind, till I suspected the state of 

 matters and prepared a fresh stock, with which satisfactory 

 results were at once obtained. The paper was kept between 

 the leaves of a book, and was dry and exposed to very little 

 rubbing. Could it have been that in course of time the 

 desiccation of the bacteria became so complete as to be 

 incompatible with continued vitality ? Whatever the reason, 

 it seems to follow that this particular species of bacterium 

 cannot be kept in the dried state for very long periods 

 without losing its vitality. 



The other point is also, I think, of some interest, as show- 

 ing the varying capacity of resistance offered to disinfecting 

 processes by the germs of different low vegetable organisms. 

 On a good many of the pieces of the paper which did not cause 

 opalescence of the solution there appeared a copious growth 

 of white mould, apparently the ordinary penicillium. The 

 spores must have fallen on the paper at the time when it was 

 exposed to the air, and they must have been subjected to the 

 same destructive influences as the bacteria; and as they 



