158 THE BLOOD. 



up by the blood in the system. From this point of view it 

 does not seem entirely unprofitable to look after the cause of 

 the coagulation of the blood. It was with such an idea as 

 this that almost the first definite experiments which we have 

 on the cause of coagulation, were performed. These consti- 

 tute the basis of the Astley Cooper prize essay for 1856, and 

 if they be not sufficient to convince all physiologists, must 

 be acknowledged to settle many points with reference to the 

 question under consideration. Dr. Richardson has here given 

 us the only definite and probable explanation of this phenom- 

 enon that has ever been presented. 1 



The views of Richardson, and the experiments on which 

 they are based, are briefly the following : 



Taking as a point of departure the fact, which, as we have 

 already seen, is sufficiently proven, that all circumstances 

 which facilitate the separation of volatile elements from the 

 blood hasten coagulation, Richardson attempted to show 

 that the volatile substances which thus escape, if retained, or 

 if made to pass through blood, will retard or arrest coagulation. 

 His experiments on the prevention of exhalation are very 

 satisfactory. The jugular vein is laid bare ; a portion of it, 

 filled with blood, is included between two ligatures, then 

 separated from the body and drawn under mercury in a U 

 tube, the vein being allowed to remain in the bend of the 

 tube for from nine to twenty-four hours. At the end of this 

 time it is removed, the blood let out, and exposed to the air. 

 In a number of experiments he found the blood entirely fluid 

 when drawn from the vein immediately after removal from 

 beneath the mercury, while it coagulated firmly in a few 

 minutes after exposure to the air. 2 This simple experiment 

 we have repeated with the same result. It shows conclusively 

 that coagulation. of the blood is not a consequence of simple 

 rest, or lowering of temperature, and that it is not kept fluid 

 in the organism by any vital influence. 



1 RICHARDSON, The Came of the Coagulation of the Blood, London, 1858. 

 " Ibid., p. 204 et seq. 



