266 Value of Antiseptics 



return of the tube to the rack require about fifteen seconds at the 

 hands of an expert manipulator, the ten tubes in the series comprise 

 the maximum number that can be handled. 



The illustration shows one of the racks, and indicates how the 

 tubes are placed in ten rows of six each, each row with an. empty 

 hole on the left. As the first tube, of each series is inoculated, it 

 is stood in the left-hand empty hole, the second stood in the hole 

 from which the first was taken, the third in that from which the 

 second was taken, and so on, so that there is always an empty 

 hole to show the operator which tube to take up for the next inoculation : 



The Technic of Determining the Phenol Coefficient. — ^Everything' 

 being ready as outHned above, one proceeds as follows: The twenty- 

 four hour bouillon culture of B. typhosus is shaken, then poured 

 through a sterile filter-paper in a sterile glass funnel and caught in 

 a sterile tube. In this way clumps of bacteria are removed and 

 uniformly distributed bacteria secured for addition to the "seeding 

 tubes." 



Exactly 5 cc. of each dilution of the disinfectant to be tested is 

 now measured into a seeding tube. To economize glassware the 

 same pipet may be used for a whole series, by beginning at the lowest 

 dilution, measuring out the necessary 5 cc. into the first seeding tube, 

 with a 5-cc. delivery pipet. The contents of the pipet are then thor- 

 oughly blown out, and a pipetful of the next weaker dilution taken 

 up to wash out the pipet. After this has been thoroughly blown 

 out and thrown away, a pipetful of this second strength of diluted 

 disinfectant is carefully measured into a second seeding tube, 

 after which the same is done with each remaining dilution in turn. 

 Th« tubes are so marked and so arranged in the rack of the water- 

 bath that no mistake can be made in transplanting from them in 

 regular order later. As each tube is fiUed, the stopper is replaced 

 and when aU have been filled and stood in the rack, it is placed in 

 the water-bath and the temperature raised to 2o°C. Anderson and 

 McCUntic do not use cotton plugs" for the seeding tubes but sterilize 

 them, open end down in a paper-Uned wire basket. Some feel 

 safer, however, in using tubes with plugs. The culture now being 

 filtered, and the seeding tubes each with the required 5 cc. of each 

 dilution of the disinfectant to be tested, all at 2o°C. in the water- 

 bath, the -subculture tubes marked and stood in their respective 

 places in the racks, sterilized pipets at hand, and four or six platinum 

 loops on the block ready steriUzed, with the burner in place ready to 

 re-sterilize them, the technic is continued by the addition of the cul- 

 ture to the seeding tubes. At this point one should make a slight 

 calculation : if the culture is to be added to each of ten of the seeding 

 tubes, it must be done before the expiration of 150 seconds or two and 

 one-half minutes for at the conclusion of that time, the first trans- 

 plantation from each seeding tube to a culture tube must take 

 place. We have averaged fifteen seconds for each operation. If 



