56 LABORATORY EXERCISES IN BACTERIOLOGY. 



but varying number of layers of blanket cloth, and distributed to the 

 top, floor, and middle height of a room of known dimensions, which has 

 previously been prepared as above outlined for the prevention of the 

 escape of the disinfectant gas used. Formaldehyde is generated by any 

 convenient form of generator and passed in the above-mentioned pro- 

 portion into the interior of the room, which is thereafter kept closely 

 sealed for twenty-four hours, then opened and well aired. As soon as 

 convenient the room is entered and the packages containing the infected 

 slips of paper removed and inoculations made therefrom into sterile 

 bouillon, the tubes marked, placed in the incubator, and observations 

 made after the first, second, and third days and the results recorded. 



Exercise 21. The above experiment is to be repeated, substituting 

 sulphurous oxide for the formaldehyde gas, 



Risumi. From the foregoing exercises it should be possible to come to fair con- 

 clusions as to the relative merits of the various methods of sterilization suggested ; and 

 it is expected, therefore, that the student will in review calculate the actual number and 

 percentage proportion of successful sterilizations accomplished by the class in the vari- 

 ous full applications of heat, and by nitration and chemical disinfection. 



