METHODS OF ANIMAL EPXERIMENTATION 139 



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. McCras's method' is easier and more satisfactory. 

 (Fig. 60.) 



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 fiUed with water and boiled in a 

 test-tube with water. The melted gelatin is removed from the inside of the capsule 



dizzxiaij 



Pig. 60. — Method of making collodion capsules. {After McCrm.) 



by means of a fine pipette. The capsule 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 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 of making collodion sacs recommended by Gorsline' 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. 



Collodion capsules are ordinarily placed free in the peri- 

 toneal cavity of the animal, by an aseptic laparotomy. The 

 wound is sutured with silk or catgut and dressed with sterile cotton 

 and collodion. 



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



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

 Arbor, 1903, p. 390. 



