METHODS OF CULTURE AND OF EXAMINATION. 89 



bouillon or water, and a small amount of the emulsion is 

 removed with the heated platinum wire. If the substances 

 to be examined are particularly tough, it is well to render a 

 mortar and pestle germ-free by dry sterilization or by ex- 

 posure to the flame, and to cover the mortar with sterile 

 paper, in the middle of which is an opening for the handle 

 of the pestle. The material is now rubbed up with the 

 pestle until a thoroughly homogeneous emulsion is made, 

 while, at the same time, the overlying sheet of paper pre- 

 vents the entrance of germs from the air. 



The tube containing the liquefied gelatin is taken in the left 

 hand with its palm directed upward, and between the thumb 



Fig. 19. Manner of holding tubes for inoculation. 



and the index-finger ; then, with a slight rotatory move- 

 ment, the cotton stopper is removed with the right hand, and 

 placed with its free extremity, which always projects from 

 the mouth of the tube, between the .index-finger and the mid- 

 dle finger of the left hand. (Fig. 19.) The platinum needle, 

 laden with the well-divided material for examination, is 

 introduced into the nutrient gelatin, great care being taken 

 to avoid bringing the wire into contact with the walls of 

 the tube. The platinum wire is withdrawn and immedi- 

 ately sterilized in the flame. The material introduced is 

 admixed with the liquefied gelatin, as intimately and as 

 evenly as possible, by means of repeated shakings, rotation, 

 inclination, and sudden straightening of the tube, now again 



