H. WORMALD 241 



VI. Effect of Desiccation. 



Small circular cover-glasses were cleaned and placed in absolute 

 alcohol. When required they were removed from the alcohol with 

 flamed forceps, rapidly dried over a bunsen flame, then passed once 

 or twice through the flame and placed in a sterile petri dish. A celery 

 extract culture, two weeks old, was shaken to distribute the sediment 

 throughout the liquid, then drops were transferred with a platinum loop 

 to the cover-glasses on which they were spread and allowed to dry at 

 the temperature of the laboratory, viz. 15° C. Two of the cover- 

 glasses were taken up with flamed forceps when the smear was only 

 about half dry and each was dropped into a tube of a culture solution. 

 The rest were kept under careful observation and when the last visible 

 trace of moisture had disappeared from any one smear the time was 

 noted. Two were dropped into tubes of the culture solution when 

 just dry, others at quarter hour, half hour and one hour respectively 

 after first appearing dry. All the tubes were then incubated. 



The result was as follows: — 



Condition of tubes after receiving the cover-glasses 



When the film was not quite dry the result, as was to be expected, 

 was as in an ordinary inoculation. Growth was retarded if the film was 

 allowed to become dry even for a few moments and an hour's desiccation 

 killed the organism. 



In a similar experiment performed when the laboratory was at a 

 higher temperature, viz. 18° C, desiccation for half an hour was sufii- 

 cient to render the cover-glasses sterile. 



A variation was also adopted by sterilizing and thoroughly drying 

 test tubes which were incubated for a short time until they had acquired 

 the temperature of the thermostat, i.e. 25° C, when smears were made 

 near the bottom of each and allowed to dry at the same temperature. 

 A few cubic centimetres of sterile celery extract were then added to 

 each at periods varying from the time when they were just dry to one 

 hour afterwards. No growth occurred in any of the tubes, so that it 



