106 MANUAL OF BACTERIOLOGY. 



is any possibility of these having accidentally come in contact 

 with any of the diseased tissues. 



Collodion Capsules. Bacteria may be cultivated in the 

 living body of an animal, without infecting the animal, when 

 they are enclosed in collodion capsules. Their soluble products 

 are able to diffuse through the collodion, while the animal's 



) 



FIG. 38. Method of making collodion capsules. (After McCrae.} 



fluid 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 were originally made by dipping the round end of a glass rod 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* is easier and 

 more satisfactory. (Fig. 36.) 



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 o f the 

 capsule by means of a fine pipette. The causule is partly filled with water or 

 broth and sterilised. 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 liours. No growth should occur outside the capsule if it is tight. 

 It may now be placed in the peritoneum of an animal. 



A method for making collodion sacs recommended by Gorslinef 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. 



There are also various other methods recommended for making collodion sacs. 



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



fSee Contributions to Medical Research. Dedicated to Victor C. Vaughan, 

 1903. 



