166 STERILIZATION AND DISINFECTION 
twenty dilutions, eighty tubes are numbered serially and placed in the 
rack which is placed conveniently at the worker’s left hand. 
Bunsen Burner. A Bunsen burner with a fantail top is led from 
the left and back of the bench with a little spare tubing. 
Loop Rack. This is made of four pieces of $-in. wood, each 4 ins. 
by 9 ins. joined in a frame so that the top is about 10 ins. high. The 
top is provided with about six grooves for the loops. The latter are 
placed in their grooves and the rack is placed in front of the worker’s 
right shoulder, close to the front of the bench and almost at right angles 
to the front edge but with a slight slant to the right and rear. The 
loops point to the left and the fantail burner is so adjusted as to prop- 
erly envelop the loop which is over it. The loops are used in succession 
and, after each one is returned to its place, the burner is moved under it 
thus providing at all times for a sterile and cool loop. 
Loops. ‘The loops used for transferring the culture after exposure 
to the disinfectant are made as follows: A close cylindrical spiral is 
made by winding nichrome wire No. 23 B. & 8., as tightly as possible 
about a piece of steel or other hard wire having a diameter of .072 in. 
(B. & S., No. 18). Wind about five full turns, bend the remainder of 
the wire sharply at a right angle to the wound portion and parallel to 
the axis of the cylinder. Remove from the core and cut off the lower 
end to leave exactly four complete turns. When completed the suc- 
cessive turns of the spiral must touch one another continuously. 
Seeding Tubes. The characters of the seeding tubes to be used 
depends entirely upon local conditions. In places in which there is 
any doubt as to air contamination cotton plugged tubes are to be pre- 
ferred. However, under conditions as exist in most laboratories the 
open seeding tubes recommended in the present standard methods are 
most convenient and quite satisfactory. 
Seeding Tube Holder. Cut down an oblong wire test-tube basket 
to about 2.5 ins. in depth and to the top fit a piece of $-in. wood through 
which three rows of seven holes each have been bored, the holes being 
of proper size to accommodate the tubes loosely. An ordinary tripod 
is used to support this rack in the water bath. The legs of the tripod 
are cut so that the tops of the seeding tubes are a little above the sur- 
face of the water. 
Inoculator. The inoculations of the diluted disinfectant with the 
culture are made with an apparatus described by Rosenau (Hyg. Lab. 
Bull. 21, p. 60). A capillary pipette graduated in tenths c.c. is fitted 
with a rubber bulb and clamped to a ring stand. The bulb is actuated 
by a second spring clamp the jaws of which engage it. This apparatus 
