170 STERILIZATION AND DISINFECTION 
final test, a closer range may be obtained by restricting the test to fewer 
columns and using the middle row of dilutions together with the top row. 
The seeding tubes having been properly sterilized are brought to 
the bench and placed in the seeding racks to the number required. 
Five c.c. of each of the dilutions of phenol and disinfectant to be tested 
are placed in order in these seeding tubes, which are appropriately num- 
bered, a separate 5-c.c. delivery tube being used for each dilution. The 
tube containing the filtered culture is next placed in one of the holes of 
the seeding-tube holder which is then placed in the water bath and 
allowed to stand there for sufficient time to bring the contents to tem- 
perature. The inoculator is then filled with culture and, at the beginning 
of an even five-minute period the first seeding tube is inoculated with 
0.1 e.c. of culture and the succeeding tubes are then inoculated at 
appropriate intervals. If the manipulator js sufficiently skilled to make 
inoculations and transfers at fifteen-second intervals the total number 
of dilutions including the phenol dilutions that can be carried through 
a test simultaneously is 20. Five of these are necessary for the phenol, 
1: 80 to1 : 120, inclusive, leaving a maximum of 15 for the disinfectant. 
This will permit the employment of two of the columns of the table of 
final dilutions, if necessary. In practice, however, it will seldom be 
found necessary to extend the range over more than one complete col- 
umn or eight dilutions which with five phenol dilutions gives thirteen 
in all. This will permit the making of inoculations and transfers at 
twenty-second intervals, with one minute leeway at the end of each 
round, a safer and more comfortable schedule. For the beginner thirty- 
second intervals are recommended which permit the carrying of ten 
dilutions simultaneously. Whatever the interval decided upon it is 
quite desirable that a plan of the test showing the dilutions to be used, 
intervals between inoculations, and times of making subcultures be 
carefully laid out on paper so that there shall be no confusion in these 
matters during the actual test. 
When the tubes have been inoculated, the inoculator is pushed away 
diagonally and the loop holder is drawn up to the edge of the bench and 
just before the expiration of the time interval, subculture tube No. 1 
is taken in the hand, the plug withdrawn, and a loop dipped perpen- 
dicularly into the first seeding tube. At the expiration of the time 
interval, the loop is withdrawn, and the transfer consummated. The 
loop is returned to its groove on the loop holder, the burner moved in 
place under it and the subculture tube given a rapid whirling movement 
to mix its contents and replaced. Another tube and another loop are 
then taken in hand for the next transfer. At the completion of the test 
