CENTBIFUGAL MACHINES 33 



Gartner's centrifuge consists of a case of sheet brass 

 with a movable cover. The bottom is shaped like the surface 

 of a very flat cone, and carries clamps for small test-tubes, 

 which are laid in with their mouths towards the centre, 

 and are so far filled with the fluid to be treated that 

 none flows out when the tubes are placed in the slanting 

 position. Six to eight samples can be centrifuged at the 

 same time. As soon as the glasses are in position, the 

 cover is lowered and fastened down by means of a bayonet- 

 catch. The centrifugal machine has for its axis a spindle 



Cover 



- Hole for the end 

 of the catgut 



FIG. 21. GARTNER'S CENTRIFUGE. 



revolving with very little friction in sockets in a cast-iron 

 frame, which serves to fasten the entire apparatus to a 

 table or a window-sill. A hole is perforated in the lower 

 part of the spindle, into which the end of a catgut string 

 is introduced, the string itself being wound round the shaft. 

 By pulling away the string the apparatus is put in rotation 

 after the manner of a child's top, the number of revolutions 

 at starting reaching over 3,000 in the minute, and the 

 motion keeps up with gradual slackening for ten to fifteen 

 minutes (fig. 21). For decanting the supernatant liquid 



