276 Experimentation upon Animals 



If the bacteriologic examination cannot be made at once, 

 the organs to be studied should be removed with aseptic pre- 

 cautions, wrapped in a sterile towel or a towel wet with a 

 disinfecting solution, and carried to the laboratory, where 

 the surface is seared and the necessary incisions made with 

 sterile instruments. 



Fragments intended for subsequent microscopic examina- 

 tion should be cut into small cubes (of i c.c.) and fixed in 

 Zenker's fluid or absolute alcohol. (See page 179.) 



Collodion capsules are quite frequently employed for the 

 purpose of cultivating bacteria in a confined position in the 

 body of an animal, where they can freely receive and utilize 

 the body- juices without being subjected to the action of the 

 phagocytes. In such capsules the bacteria usually grow 

 plentifully, and not rarely have their virulence increased. 



The capsules can be made of any size, though they are 

 probably most easily handled when of about 5-10 c.c. capac- 

 ity. The size is always an objection, because of the dis- 

 turbance occasioned when they are introduced into the 

 abdominal cavity. 



The capsules are made by carefully coating the outside of 

 the lower part of a test-tube with collodion until a suffi- 

 ciently thick, homogeneous layer is formed. During the 

 coating process the tube must be twirled alternately within 

 and without the collodion, so that it is equally distributed 

 upon its surface. When the desired thickness is attained, 

 and the collodion is sufficiently firm, the tube is plunged 

 under water and the hardening process checked. 



A cut is next made around the upper edge of the collodion: 

 film, and it is removed by carefully turning it inside out. In 

 this manner an exact mold of the tube is formed. If a small 

 opening be made at the end of the tube over which the sac is 

 molded, and the tube filled with water after being properly 

 coated with collodion, a small amount of pressure, applied 

 by blowing gently into the tube, will force the water between 

 the collodion and glass and so detach it without inversion. 

 A test-tube of the same size is next constricted to a degree 

 that will not interfere with the future introduction of culture 

 media in a fine pipet or inoculation with a platinum loop, 

 and that will permit of ready sealing in a flame when neces- 

 sary ; the rounded end is cut off, and the edges are smoothed 

 in a flame. The upper open end of the collodion bag is care- 

 fully fitted over the end of the tube, shrunk on by a gentle 



