Testing Germicidal Value of Liquids 259 



15 seconds, the operator must have every detail of the technic 

 so well in hand, and the materials so conveniently placed, etc., 

 that he can complete the entire performance of the technic from 

 the addition of the culture to the seeding tubes to the last trans- 

 plantation from seeding tubes to subculture tube without a hesita- 

 tion and without a distraction. It is on account of the necessity of 

 this "continuous performance" that such care was taken to point 

 out the exact details of apparatus and materials needed, before 

 describing the technic. 



To return to the seeding of the tubes, a sterile pipet graduated 

 in Y\ o cc - is used. The cotton stoppers are removed from the 

 seeding tubes and thrown away as of no further use. One by 

 one as the time arrives, tubes are taken in one hand, inclined to 

 an angle of about 45 degrees, while the tips of the pipet are lightly 

 touched to that side of the tube from which the fluid has run 

 away on account of the slanting, and exactly o.i cc. of the cul- 

 ture delivered. This may under no circumstances take longer 

 to perform than 15 seconds, and if one succeed in finishing it 

 in a shorter time, he must wait until the calculated time arrives 

 before delivering the culture into the next tube and so on until 

 the end is reached. Each tube is given three gentle shakes after 

 being straightened up, then returned to the water-bath. 



With a ten-tube series, and a time allowance of 15 seconds for 

 each tube, the entire series of tubes is no sooner completed than 

 the time (2^ minutes) for making the first series of transplanta- 

 tions to the subculture tubes has arrived. The operator therefore 

 seizes at once the first of the culture tubes in the 2j^-minute series 

 with one hand, and a sterile platinum loop with the other. He 

 cautiously removes the cotton plug from the culture tube, and 

 at the proper moment introduces the platinum loop into the first 

 seeding tube all the way to its bottom, withdraws it, and carries 

 one drop of the contained fluid into the first subculture tube which 

 he plugs and places in the empty hole to the left of the row in the 

 block, at once taking up its neighbor on the right. As only 15 

 seconds are allowed for each such transfer, the operator must pro- 

 ceed without hesitation. There is no time to sterilize the platinum 

 loop, so he lays it on the block, pushes the flame under it and takes 

 up an already sterilized loop with which he performs the same act 

 of transplantation for the second tube that was done for the first, 

 doing it on the appropriate second of time, and so continuing 

 through the whole series. 



Every test of the phenol coefficient of disinfection must em- 

 brace two such series, one made with the dilutions of the phenol 

 that is to act as the standard, the other made with the dilutions of 

 the disinfectant to be determined. If, however, a variety of dif- 

 ferent germicides are to be tested the same day, one phenol test 

 will answer the requirement of the whole group. The following 



