LESSON III. 



COAGULATION OF BLOOD. CHAEACTERS 

 OF PROTEIDS: 



1. Observe the ooagulation of freshly shed blood * ; 

 it is at first fluid but soon passes iato 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 fi:om the vessel squeez- 

 ing out more and more serum. 



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

 shed blood'; 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. 



