LESSON III. 



COAGULATION OF BLOOD. CHARACTERS 

 OF PROTEIDS. 



1. Observe the coagulation of freshly shed blood 1 ; 

 it is at first fluid but soon passes into a jelly 

 which gradually becomes firm; if then placed 

 aside for some time, drops of clear serum will, 

 by the shrinking of the fibrin, be pressed out on 

 the surface of the clot; later the clot shrinks 

 more or less completely from the vessel squeez- 

 ing out more and more serum. 



2. With a feather stir slowly about 10 c.c. of freshly 

 shed blood 1 ; a considerable portion of the blood 

 will form a clot on the feather ; squeeze out the 

 clot under a stream of water from a tap; the 

 clot shrinks considerably and a small quantity 

 only of fibrin is obtained. 



3. Repeat 2, but this time stir quickly, filaments 

 of fibrin will be obtained ; note that the fibrin is 

 extensible and elastic; leave the defibrinated 

 blood for a day, no further clot is produced. 



1 This will be obtained by the Demonstrator. 



