157 



LESSON XXI 

 COAGULATION OF BLOOD 



1. Salted plasma and oxalate plasma are the two kinds of blood-plasma, 

 which are most easUy prepared (Lesson IX.). The separation of the plasms 

 and corpuscles may most readily be carried out by the centrifugal machine 

 (one form of this is represented in the next figure) ; the corpuscles settle and!, 

 the supernatant plasma is pipetted off. 



Fig. 60. — Centrifugal machuio as maile by Ruone of Heulelba-g. Glass vessels containing the sub- 

 stances to be centiifngalised are placed within the six metallic tabes which hang vertically while 

 the disc is at rest ; when the machinery is set going they fly out into the horizontal position. A. 

 water motor or gas engine may be used to work the instmment. A. small bat effective hand- 

 centrifuge is made by Watson, Laidlaw, & Co., Glasgow. 



The principal properties of these two forms of plasma have already been 

 described in Lesson IX. ; the following additional experiments may now be 

 performed. 



2. Heat a portion of the salted plasma to 60° C. The fibrinogen is 

 precipitated (coagulated by heat) at 56° C. Filter. Dilute the filtrate as in 

 Lesson IX. 3, and add fibrin ferment. No coagulation occurs. 



3. Oxalate plasma or decalcified plasma coagulates when a little calcimn 



