240 



BACTERIOLOGICAL METHODS 



fourteen holes each, are used for holding the subculture tubes, 

 and as plants are made from each mixture of culture and dis-j 

 infectant every 2% min. up to 15 min., six tubes are required for j 

 each dilution. Thus in each rack we have ten rows of six tubes j 

 each with two empty cross rows of holes left, which are utilized 

 by placing over in the next row each tube as it is planted. This 

 makes it easy to keep run of the tubes that are planted. It isj 



FIG. 86. Cross section of water bath showing seeding tubes in position. 

 (Anderson & McClintic, Hygiene Laboratory Bulletin No. 82, U. S. Public Health 

 Service.) 



well also always to plant from the seeding tube in a certain hole 

 in the water bath into a certain row of tubes in the rack. This, 

 after a little practice, will help to avoid errors in planting. 



Method of Conducting the Test. If there are in one experi- 

 ment more than ten dilutions of the disinfectant, including the 

 phenol controls, the stronger solutions of the disinfectant and 



