Collodion Sacs fal 
water. The liquid gelatin is pipetted off. The apparatus is sterilized 
and prepared for introduction into the animal’s body in the afore- 
described manner. 
Grubbs and Francis” utilized the perforated tube heretofore re- 
ferred to, the openings of which are obliterated with gelatin. The 
outside of this tube is coated with several layers of collodion and the 
gelatin removed by means of hot water. 
The method of preparing collodion sacs as carried out by the 
Pasteur Institute is difficult. The difficulty is in separating the col- 
lodion casing from the glass tube. Gorsline” has overcome this and 
by his method the sac can be prepared with ease. He selects a tube, 
which may be a test tube, with a 2 mm. opening in its rounded end. 
The opening is closed with a thin film of collodion. The tube is then 
rotated in the collodion in the usual way. The sac is removed from the 
glass tube by filling the tube with water. By constant blowing the 
water is forced through the opening, allowing it to run between the 
outside wall of the tube and the inside of the sac, and thus separating 
the latter from the former. The top of the sac is cut loose from the 
tube and the sac is slipped off. It is then immersed in water. Its 
subsequent preparation is similar to that previously described. 
The method of preparing the collodion sae for this work is that of 
Gorsline slightly modified. The technique of sealing the sac containing 
the suspension of micro-organisms, however, is entirely different from 
that described by other experimenters. 
The procedure of preparing these sacs is as follows: Freshly pre- 
pared collodion is used, the consistency of which depends upon whether 
or not very thin or thick walled sacs are desired. This may be regu- 
lated by diluting with a mixture of equal parts of alcohol and ether or 
by exposing in the air and allowing it to evaporate. This solution must 
be free from bubbles. A clean tube about 300 mm. by 8, 10, 14, 16 
18 mms. with one end rounded with a small opening (2-4 mm.) in the 
center is used. The outside of the tube is wiped perfectly dry after being 
moistened with a five per cent glycerin solution. This leaves a very 
thin film of glycerin on the wall of the tube and facilitates removing 
the collodion covering from it. 
The opening in the end of the tube is closed by painting it over 
with a film of collodion and allowing it to dry for about one minute. 
The tube is rotated several times in the collodion, which is in a glass cyl- 
inder inclined at a desired angle. The tube is then withdrawn, care 
being taken that it does not come in contact with the glass container. 
It is rotated in a horizontal position until the collodion hardens. If 
a thick walled sac is to be made this process may be repeated several 
times. The collodion-covered tube is then held under the tap and water 
is run onto it. By filling the tube with water and by blowing, the sac 
is removed as in the Gorsline method. At this stage if the collodion 
10 Bulletin No. 7 of the Hygiene Laboratory of the U. S. Marine Hospital Service 
—1902. 
11 Contributions to Medical Research, dedicated to Victor Clarence Vaughan by 
colleagues and former students of the Department of Medicine and Surgery of the 
University of Michigan, pp. 391-393—19038. 
