44 8 



BACTERIOLOGICAL ANALYSES 



(b) The handle employed should be provided with 

 a special fastening (e. g., a clutch similar to 

 that employed for the free wheel of a 

 bicycle), or should be readily detachable so 

 that, on ceasing to turn, the handle should 

 not, by its weight and air resistance, act as a 

 brake and stop the' machine too suddenly. 

 One of the few satisfactory machines of this class is shown 

 in figure 212. 



FIG. 212. Electrically driven centrifugal machine, with flexible 

 (broken) spindle encircled by the field magnets of the motor. 



Sterile centrifugal tubes, of some 60-70 c.c. capacity, tapering 

 to a point at the closed end, plugged with cotton-wool. 



Small centrifugal machine to run two tubes of 10 c.c. capacity 

 at 2500 to 3000 revolutions per minute preferably driven by 

 electricity, of the type figured on page 327 (Fig. 162). 



Sterile centrifugal tubes of 10 c.c. capacity with the distal 

 extremity contracted to a narrow tube and graduated in hundredths 

 of a cubic centimetre (Fig. 213). 



Sterilised cork borer. 



Case of sterile pipettes, 10 c.c. (in tenths of a cubic centimetre). 



