150 THE BLOOD. 



Coagulation of the Blood in ilie Organism. 



The blood coagulates in the vessels after death, though 

 less rapidly than when removed from the body. As a gen- 

 eral proposition it may be stated that this takes place in from 

 twelve to twenty-four hours after circulation has ceased. 

 Under these circumstances it is found chiefly in the venous 

 system, as the arteries are generally emptied by post mortem 

 contraction of their muscular coat. Coagula are found, how- 

 ever, in the left side of the heart and in the aorta, but they 

 are much smaller than those found in the right side of the 

 heart and the large veins. These coagula present the general 

 characters we have already described. They are frequently 

 covered by a soft whitish film, analogous to the butfy coat, 

 and are dark in their interior. 



It was supposed by John Hunter that coagulation of the 

 blood did not take place in animals killed by lightning 

 hydrocyanic acid, or prolonged muscular exertion, as when 

 hunted to death ; but it appears from the observations 

 of others that this view is not correct. J. Davy reports a 

 case of death by lightning where a loose coagulum was found 

 in the heart twenty-four hours after. In this case decompo- 

 sition was very far advanced, and it is probable that the 

 coagula had become less firm from that cause. His obser- 

 vations also show that coagulation occurs after poisoning by 

 hydrocyanic acid, and in animals hunted to death. 1 



Coagulation in different parts of the vascular system is 

 by no means unusual during life. In the heart we sometimes 

 find coagula which bear evidence of having existed for some 

 .time before death. These were called polypi by some of the 

 older writers, and are often formed of fibrin almost free from 

 red corpuscles. They generally occur when death is very 

 gradual, and the circulation continues for some time with 



1 DR. JOHN DAVY, Researches Physiological and Anatomical, vol. ii., p. 70 

 el xeq. 



