Testing Germicidal Value of Liquids 



26s 



to the germicidal solutions is to take place, have already been pro- 

 vided for in the construction of the water-bath. 



For the "subculture" tubes, any test-tube rack will do, but it 

 is more convenient to have a special rack or stand made. That 

 recommended contains five rows of 14 holes each. Each tube of 

 culture-medium is carefully marked with a blue pencil to show three 



Fig. 86. — Block for subculture tubes (Anderson and McClintic, in Bulletin 

 No. &2, Hygienic Laboratory). 



Fig. 87. — ^Device for flaming inoculating loops (Anderson and McClintic, 

 in Bulletin No. 82, Hygienic Laboratory). 



things, I, the germicide; 2, the dilution; 3, the time of exposure, and 

 stood in its place in the rack as will be explained below. 



The transplantations from the seeding tubes to the culture tubes 

 are to be made every two and one-half minutes up to fifteen minutes, 

 so that for each strength of dilution to be tested, there wiU be six 

 tubes. In addition to these test-tubes there will be four dilutions 

 of phenol to act as controls so that every two and one-half minutes 

 ten transplantations must be made. 



As two and one-half minutes contain 150 seconds, and as the 

 picking up and opening of the subculture tube, the transfer of the 

 seed-culture to the medium, the replacement of the stopper and the 



