688 BACTERIA IN AIR, SOIL, WATER, AND MILK 



such as that devised byFraenkel, maybe used. This consists of an iron 

 rod the lower end of which is pointed. Just above the point a movable 

 collar is fitted. This collar has a slit-like opening. The rod beneath the 

 collar has a deep longitudinal groove corresponding to the slit in the 

 collar. A flange on the collar permits opening and closing of the groove 

 while the instrument is below the ground. The drill is forced into the 

 earth to the desired depth, the groove is opened and earth is forced into 

 the chamber by twisting the rod. In the same manner the groove may 

 be closed. The soil obtained in this way is taken out of the chamber 

 and a definite quantity, say one gram, is dissolved and washed thor- 

 oughly in a measured volume of sterile water or sterile salt solution. 

 Fractions of this are then mixed with the culture medium, plated, and 

 cultivated aerobically or anaerobically as desired. 



