WHIPPED BLOOD. 181 



vessel to be pulled away, and thus the first sign of the 

 contraction of the fibrin is seen in the cupping of the sur- 

 face of the gelatinized blood where the threads have no 

 solid attachment, and there the contracting mass presses 

 out from its meshes "the first drops of serum. Finally the 

 contraction of the fibrin overcomes its adhesion to the vessel, 

 and the clot pulls itself loose on all sides, pressing out 

 more and more serum. The great majority of the red cor- 

 puscles are held back in the meshes of the fibrin. 



Whipped Blood. The essential point in coagulation 

 being the formation of fibrin in the plasma, and blood only 

 forming a certain amount of fibrin, if this be removed as fast 

 as it forms the remaining blood will not clot. The fibrin 

 may be separated by what is known as <e whipping" the 

 blood. For this purpose fresh drawn blood is stirred up 

 vigorously with a bunch of twigs or a bundle of wire, and 

 the sticky fibrin threads as they form adhere to these. . If 

 the twigs be then withdrawn a quantity of stringy material 

 will be found attached to them. This is at first colored red 

 by adhering blood-corpuscles, but by washing in water they 

 may be removed; the pure fibrin thus obtained is perfectly 

 white and in the form of highly elastic threads. The 

 " whipped" or " defibrinated blood" from which the fibrin 

 has been in this way removed looks just like ordinary 

 blood, but has lost its power of coagulating spontaneously. 



Uses of Coagulation. The living circulating blood in 

 the healthy blood-vessels does not clot; it contains no solid 



Why is the first sign of their contraction seen in the cupping? 

 What is the final result of this contraction? Why is the clot red? 



How can we prevent blood from clotting? How is blood 

 whipped? What do we find on examining the twigs after whipping 

 blood? How may we get the pure fibrin? What are its characters? 

 Give another name for whipped blood. How does it differ from 

 ordinary blood? 



