rvals of 2-1/2, 5, 25 and 30 minutes.

9. Take up 0.5 c.c. of B. coli emulsion in sterile pipette graduated in
tenths of a cubic centimetre and stand by.

10. As soon as the bell rings lift the pipette from tube A with the left
hand and from the charged pipette held in the right hand deliver 0.1
c.c. of B. coli emulsion into the 1:100 solution. Then replace the
pipette and washer.

[Illustration: FIG. 219.--Test-tube rack.]

11. Raise the tube with the left hand and shake it to mix germ and
germicide, whilst returning the delivery pipette in the right hand.

12. Repeat the process with tubes B, C, D and E; then drop the infected
delivery pipette in the lysol jar. The inoculation of the five tubes can
be carried out very expeditiously, but a period of 10 seconds must be
allowed for each tube.

13. When the bell rings at 2-1/2 minutes blow through the pipette in
tube A (this agitates the germ + germicide mixture and ensures the
collection of a fair sample); allow the mixture to enter the pipette,
and as the column of fluid extends well above the terminal graduation,
the right forefinger adjusted over the butt-end of the pipette before it
is lifted will retain more than 0.1 c.c. of the mixture within the bore
when the point of the pipette is clear of the fluid in the tube. Touch
the point of the pipette on the inner wall of the tube, and allow any
excess of fluid to escape, only retaining 0.1 c.c. in the pipette.

14. At the same time, with the left hand remove Bile Salt Tube No. 1
from the upper tier of the rack, take out the cotton-wool plug with the
hand already holding the pipette (the relative positions of pipette,
plug and culture tubes being practically the same as those of platinum
loop, plug and culture tube shown in Fig. 68, page 74).

15. Insert the point of the pipette into the subculture tube, and blow
out the mixture into the medium--replug the tube and drop it into the
wire basket. Replace the washer-pipette in tube A.

As soon as the point of the pipette has entered the mouth of tube A it
may be released, since it has already been so adjusted that it just
clears the bottom of the test-tube, and the elastic washer will prevent
any damage to the tube.

Steps 13, 14 and 15 occupy on an average 10 seconds.

16. Repeat steps 13, 14 and 15 with each of the other tubes B, C, D and
E.

17. Repeat these various steps 13-16 when the bell rings at 5, 25 and 30
minutes.

18. Place all the inoculated tub