14 



BULLETIN 148, U. S. DEPARTMENT OF AGRICULTURE. 



contact with the air after sterilizing. A can or receptacle which 

 works very satisfactorily was devised by one of the authors (see text 

 fig. 1). This starter-can consists of two tanks (5) and (11) con- 

 nected by a block-tin collar (7) — brass can not be used, as it prevents 

 growth of the culture. In this collar is fitted a tinned plug (8), fas- 

 tened to a tinned-brass pipe (6). A brass collar (1) large enough to 



let the block-tin plug 

 pass through is fast- 

 ened at the top of the 

 upper tank. Into this 

 brass collar is fitted 

 a brass plug (2), 

 through which passes 

 the tinned-brass pipe 

 (6). Both the pipe 

 and plug are threaded 

 to permit the raising 

 and lowering of the 

 block-tin plug (8) be- 

 tween the two tanks 

 without raising the 

 brass plug in the 

 top tank. When both 

 plugs are in place 

 there should be an 

 opening in the pipe 

 at the point (4) to 

 permit the air to pass 

 from the lower tank 

 (11) to the upper 

 tank (5) when the 

 whey is passing from 

 the upper tank to the 

 lower tank. The end 

 of the brass pipe (6) 

 extending above the 

 upper tank should be plugged with cotton to prevent any outside con- 

 tamination when the starter is drawn from the lower tank. The open- 

 ing (3) in the top of the upper tank for filling is plugged with a cork 

 into which is fitted a thermometer. The pipe (12) for draining off the 

 starter is placed about one-half inch from the bottom of the lower 

 tank. This always leaves enough starter for reinoculation. The 

 lower can is insulated with a zinc jacket filled with ground cork (9). 



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s-/z 



to 



Fig. 1. — A mother-starter can for carrying pure cultures. 

 Although it was designed especially to prevent cultures 

 of Bacillus bulgaricus from yeast contamination in mak- 

 ing Swiss cheese, it can he used for all whey cultures. 



