METHODS OF ANIMAL EXPERIMENTATION 135 



able to diffuse through the collodion, while the animal's fluids may 

 pass into the sac to nourish them. These capsules were originally 

 made by dipping the round end of a glass rod into collodion 

 repeatedly. McCrae's method 1 is easier and more satisfactory. 

 (Fig. 58.) 



A piece of glass tubing is taken, and a narrow neck drawn on it near one 

 end. This end of the tube is rounded in the flame and, while still warm, the 

 body of a gelatin capsule is fitted over it, so that the gelatin may adhere to 

 the glass. The capsule is now dipped into 3 per cent collodion, covering 

 the gelatin and part of the glass. It is allowed to dry a few minutes, and is 

 dipped again. In all, two or three coatings may be given. The capsule is 

 filled with water and boiled in a test-tube with water. The melted gelatin is 

 removed from the inside of the capsule by means of a fine pipette. The cap- 

 sule is partly filled with water or broth and sterilized. The capsule may now 

 be inoculated. The narrow part of the glass tube which constitutes the neck 

 must then be sealed in the flame, taking care that the neck be dry. The 



(1 



FIG. 58. Method of making collodion capsules. (After McCra.) 



sealed capsule should be placed in bouillon for twenty-four hours. No 

 growth should occur outside the capsule if it is tight. It may now be placed 

 in the peritoneal cavity of an animal. 



A method for making collodion sacs recommended by Gorsline 2 consists 

 in the use of a glass tube, the lower end of which is rounded and closed, 

 except a small hole, which is temporarily filled with collodion. This tube is 

 dipped in collodion and dried, as above. It may now be filled with water. 

 By blowing at the opposite end, the pressure through the hole in the bottom 

 of the glass tube will cause the capsule to loosen so that it comes away easily. 

 Sacs made in this way are soaked in water for 30 minutes, dried and attached 

 to the glass tube by gentle heat. The joint is wound with silk thread and 

 coated with collodion. The sac is then filled with distilled water, immersed 

 in a tube of water and sterilized in the autoclave. 



There are also various other methods recommended for making collodion 

 sacs. 



1 Journal of Experimental Medicine. Vol. VI, p. 635. 



2 Contributions to Medical Research. Dedicated to Victor C. Vaughan, Ann 

 Arbor, 1903, p. 390. 



