BY R. GREIG SMITH. 



67 



mention that testing by means of the hanging drop is not 

 advisable when using lime salts, unless the platinum loop is 

 cleaned in hydrochloric acid after each ignition. 



Precipitation of bacteria by calcium chloride. — The results will 

 probably be best seen by looking at the following table, in which 

 the relative precipitation is indicated by numbers running from 

 1 to 6; 1 represents uniform turbidity with a very slight precipi- 

 tate, whilst 6 indicates a complete precipitation with a clear 

 supernatant liquid. The intermediate numbers represent inter- 

 mediate stages of precipitation. A zero means that no change 

 occurred, while a plus shows that flocculation was visible when 

 the liquid was examined with a hand lens : — 



It will be seen that the bacteria exhibit different susceptibilities 

 to the precipitating action of calcium chloride. Bad. typhi is 

 more sensitive than Bad. prodigiosum, and the latter than Bad. 



