70 Proceedings of Indiana Academy of Science 
one would sharpen a pencil, so as to expose the membrane lining the 
central canal. <A desirable length of this membrane is denuded. One 
end is tied firmly and by means of a glass rod it is turned inside out. 
A glass tube is fitted into the open end of the sac and fastened with 
strong thread. The sac is filled with distilled water and sterilized. 
The fluid is removed from the sterile sac and replaced with a suspen- 
sion of the organism. The sac is tied shut and the glass tube removed. 
The end is covered with melted gum lac. The thus prepared sac is 
placed in the peritoneal cavity of the animal. 
The method of preparing collodion sacs as first carried out by the 
Pasteur Institute is quite different from the present-day procedure. 
The collodion of desirable consistency, which is in a cylinder, is inclined 
at a suitable angle. A glass tube of small diameter with a closed 
rounded end is inserted into the solution and rotated until a surface 
of collodion of sufficient thickness has been deposited upon the tube. 
This tube is then rotated in the air until the collodion has set and is 
no longer sticky. 
With a scalpel the upper edge of the collodion layer is cut circu- 
larly. The thumb nail is used to turn back,upon itself this even edge 
of the collodion sac. By turning the sac inside out it can be slowly 
peeled off like a “glove finger.”” The sac is then everted and distended. 
A small piece of glass tubing is fitted into the open end of the sac and 
fastened with thread which is then coated with collodion. The sac is 
filled with water, suspended in water in a flask and sterilized. 
The water is removed from the sac with a sterile pipette and the 
suspension containing the germs under investigation introduced. The 
sac is closed with a sterile rubber stopper. This plug is dried and 
painted with collodion. Instead of closing the opening of the tube in 
this manner, the glass tube which is fitted into the sae can be drawn 
out into a capillary beforehand. After the sac has been sterilized and 
inoculated with the organism the end of the capillary tube is sealed 
in the flame, thus closing the sac. 
In view of the fact that the sae is liable to break, especially if 
kept in the animal for months, Novy’ introduced a perforated glass 
tube which has been drawn out into a capillary, into the sac. The sac 
is attached to this tube. The apparatus is sterilized, inoculated and 
sealed in the usual way. 
McCrae, and a little later Harris,’ who slightly modified the former’s 
method, prepared sacs by introducing the hot end of a small glass 
tube into a gelatin capsule. When cold the tube becomes fixed and 
is painted with moderately thick collodion which is allowed to dry. It 
is then rotated in the air so as to permit the solution to dry. This 
procedure is repeated several times until the desired thickness of col- 
lodion is obtained. 
The gelatin inside of the collodion covering is removed by intro- 
ducing hot water into the tube, and also by placing the capsule in hot 
* Laboratory Work in Bacteriology, pp. 498, 499—1899. 
8 Journ. Exp. Med., Vol. VI, p. 635—1901. 
® Eyre, Bacteriological Technique, p. 358—1913. 
