ix BACTERIA IN ICE CREAM 125 



(3) Keep the plates at the ordinary temperature, count 

 the colonies, and work them up in the ordinary manner, 

 both microscopically and by means of subcultures in 

 gelatine. 



(b) Examination for typhoid bacilli and the Bacterium coli 

 commune. 



(1) If it is desirable to test ice cream for typhoid 

 bacilli or the Bacterium coli commune, a large quantity of 

 sterile water should be added, for otherwise it will not 

 pass readily through the Berkefeld filter. 



(2) Filter through a sterile Berkefeld filter, and with a 

 brush scrape the bacteria from the candle of the filter into 

 20 to 50 cc. of sterile water in a small sterile beaker. 



(3) Work this up in the same manner as described on 

 p. 98. 



The Bacterium coli commune is frequently found in 

 ordinary street ices. 



