er of alcohol and one of water. This loosens the collodion and
allows it to be peeled off in the shape of a small test-tube.

3. Take a 20 cm. length of glass tubing, of about the diameter of the
test-tube used in forming the sac, and insert one end into the open
mouth of the sac.

4. Suspend the glass tube with attached sac, inside a larger test-tube,
by packing cotton-wool in the mouth of the test-tube around the glass
tubing, and place in the incubator at 37 deg. C. for twenty-four hours.
When removed from the incubator, the sac will be firmly adherent to the
extremity of the glass tubing.

5. Plug the open end of the glass tubing with cotton-wool, and sterilise
the test-tube and its contents in the hot-air oven.

To use the sac, remove the plug from the glass tubing, partly fill the
sac with cultivation to be inoculated, by means of a sterile capillary
pipette, and replug the tubing. When the abdominal cavity has been
opened, remove the tubing and attached sac from the protecting
test-tube, close the sac by tying a sterilised silk thread tightly
around it a little below the end of the glass tubing, and separate it
from the tubing by cutting through the collodion above the ligature, and
the sac is ready for insertion in the peritoneal cavity.

B. ~Celloidin Sacs~ (_Harris_).

_Materials Required._

Quill glass tubing.

Gelatine capsules such as pharmacists prepare for the
exhibition of bulky powders.

Various grades of celloidin, thick and thin, in wide-mouthed
bottles.

1. Take a piece of quill glass tubing some 4 cm. long by 5 mm. diameter;
heat one end in the bunsen flame.

2. Thrust the heated end of the tube just through one end of a gelatine
capsule and allow it to cool (Fig. 185).

3. Remove any gelatine from the lumen of the tube with a heated platinum
needle; paint the joint between capsule and tube with moderately thick
celloidin and allow to dry.

[Illustration: FIG. 185.--Making celloidin capsules.]

4. Dip the capsule into a beaker containing thin celloidin, beyond the
junction with the glass and after removal rotate it in front of the
blowpipe air blast to dry it evenly. Repeat these manoeuvres until a
sufficiently thick coating is obtained.

5. Apply thick celloidin to the tube-capsule joint, the opposite end of
the capsule, and the line of junction of the capsule with its cap; dry
thoroughly.

6. With a teat pipette fill the capsule (through the attached t