METHODS OF INFECTION. 



263 



succession. In this way, the syringe is heated up evenly. 

 It is then partially filled with water, placed on the syringe 

 holder (Fig. 41 c), and immersed in the boiling water. An 

 exposure for three to five minutes under these conditions 

 will be sufficient. The holder with the syringe is then re- 

 moved and the latter is allowed to cool, after which the 

 contained water is expelled. The bacterial fluid is now 

 drawn up into the syringe through the needle. If any air 

 is present this should be expelled, by holding the syringe 

 in a vertical position and applying gradual pressure to the 

 piston. Before doing this, it is advisable to pass the 

 needle through a piece of sterile filter paper, slipped over 

 the end of a wide test-tube. The latter receives the few 

 drops of liquid that are expelled at the same time with the 

 air. 



FIG. 41. a Fletcher radial burner; b Enameled stew-pan or water-bath; c Syr- 

 inge holder; ^Syringe. 



After using the syringe, it should be rinsed with boil- 

 ing water in the manner mentioned, and then immersed in 

 the boiling water and sterilized. In order to prevent rust- 

 ing of the needles, these should be kept in a 10 per cent, 

 solution of borax. 



When it is desirable to inject a relatively large quan- 

 tity of liquid into an animal, or to inject a number of animals 

 in succession with the same liquid (as in the immunization 

 of horses), then an arrangement similar to that shown in 



