CH. XXVI.] THE PLASMA AND SERUM 415 



venting the blood from coagulating. The corpuscles, being heavy, 

 sink, and the supernatant plasma can then be removed by a pipette 

 or siphon, or more thoroughly by the use of a centrifugal machine 

 (see tig. 345). 



On counteracting the influence which has prevented the blood 

 from coagulating, the plasma then itself coagulates. Thus plasma 



FIG. 845. Plan and section of centrifugal machine. A, an iron socket secured to top of table B ; c, a 

 steel spindle carrying the turntable r>, and turning freely in A ; E, a flange round turntable D ; 

 F F, shallow grooves on face of D in which the test tubes are fixed by clamps o G ; H, a pulley fixed 

 to end of spindle c, and turned by the cord K ; 1 1 are two guide pulleys for cord K. The upper part 

 of the figure is a surface view of the rotating turntable. (Gamgee.) 



obtained by the use of cold clots on warming gently ; plasma which 

 has been decalcified by the action of a soluble oxalate clots on the 

 addition of a calcium salt ; plasma obtained by the use of a strong 

 solution of salt coagulates when this is diluted by the addition of 

 water, the addition of fibrin -ferment being necessary in most cases ; 

 where coagulation occurs without the addition of fibrin-ferment no 

 doubt some is present from the partial disintegration of the. corpuscles 



