530 



BACTERIOLOGY. 



dows are securely caulked with strips of cloth, or better 

 with putty. The usual time of exposure is 20 hours. 



The formaldehyde experiments may be carried out, 

 either by sprinkling large sheets of muslin or filter-paper 



with the necessary amount of 

 the 40 per cent, solution and 

 then hanging these up in the 

 room, or by distilling the for- 

 maldehyde into the room 

 through a tube inserted into 

 the key-hole. The author's 

 apparatus 1 shown in Fig. 76 

 has been especially designed 

 for practical room disinfec- 

 tion. The copper vessel can 

 be heated with a Bunsen burn- 

 er or with a Primus kerosene 

 lamp. 150 c.c. of the 40 per 

 cent, formaldehyde solution 

 are used for each 1,000 cu. ft. 

 of air space. 



FIG. 76. The author's formaldehyde ap- ry,, , . , 



paratus for room disinfection a Narrow The bacterial Suspensions 



tube, to be inserted in key-hole; b Funnel 



tube provided with solid stopper; c Reser- are prepared according to the 



voir; d Kerosene burner. 



directions given on p. 514; 



and sterile silk-threads, muslin squares and cover-glasses 

 are then infected. The action of the disinfectant should be 

 studied, at the same time, on moist and on dry specimens. 

 The moist specimens can be kept in this condition, for hours 

 if need be, by placing them over water in a large moist- 

 chamber. The dried specimens are obtained by placing the 

 freshly prepared set in an incubator at 39 for 2-3 hours, the 

 cover of the dish being slightly ajar. When the specimens 

 have become dry they should be loosened from the bottom 

 by means of sterile forceps. 



teacher's Sanitary Bulletin, No. 3, Michigan State Board of 

 Health; Medical News, May, 1898, p. 641. 



