258 Value of Antiseptics 



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 outlined above, one proceeds as follows: The 

 24-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 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, meas- 

 uring 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 pipetf ul 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. The 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 filled, the stopper is 

 replaced and when all have been filled and stood in the rack, it is 

 placed in the water-bath and the temperature raised to 20°C. 

 Anderson and McClintic do not use cotton plugs for the seeding 

 tubes but sterilize them, open end down in a paper-lined wire 

 basket. Some feel safer, however, in using tubes with plugs. The 

 culture now being filtered, and the seeding tubes each with the re- 

 quired 5 cc. of each dilution of the disinfectant to be tested, all 

 at 20° 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 sterilized, 

 with the burner in place ready to re-sterilize them, the technic is 

 continued by the addition of the culture to the seeding tubes. At 

 this point orie 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 23.^ minutes for at the con- 

 clusion of that time, the first transplantation from each seeding 

 tube to a culture tube must take place. We have averaged 15 

 seconds for each operation. If each transfer takes an average of 



