192 



PRACTICAL PHYSIOLOGY 



corpuscles. Such blood is called defibrinated or whipped blood, and cannot 

 be made to clot by any means whatsoever, because it has already clotted 

 in the process of whipping. Besides containing fibrinogen, the plasma 

 also contains albumin and globulin, which remain unchanged during 

 clotting and pass into the serum (see proteids). 

 The following schema exemplifies the process : 



Living blood. 



1 



Albumin. Globulin. 



Ca. salts + Pro-thrombin. 

 Fibrinogen + Fibrin ferment. 1 



I 

 2nd globulin. 



i 

 Fibrin. 



I 



Serum. 



! 



Clot. 



I 

 Dead blood. 



Conditions which retard Clotting. (1) Cold receive the blood into a 

 vessel placed in ice (i.e. keep it at a temperature a little above freezing 

 point). 



(2) Contact with blood-vessel wall " Living test tube." 



(3) Addition of certain neutral salts " Salted plasma." 



(4) Addition of an oxalate "Oxalate plasma." 



(5) Addition of leech extract This is a secretion produced by the 

 salivary glands of the leech, and which can be obtained by extracting 

 the heads with water. 



(6) Contact with oil. Receive the blood into a smooth vessel smeared 

 with oil. The oil forms a layer on the surface. 



(7) Intra-vitam methods. These consist in injecting certain substances 

 into the blood-vessels of the animal before bleeding it. They seem to 

 act by depriving the blood of some of the factors necessary for clotting, 

 but their exact action is not understood. These substances are : 



(a) Commercial peptone, which consists mainly of proteoses. 

 (/?) Soap solution. 



/ y) A weak alkaline solution of nucleo-proteid injected slowly 

 " negative phase " of nucleo-proteid injection. 



1 The excess of fibrin ferment passes into the serum. 



