COAGULATION IN THE OEGANISM. 151 



greatly diminished activity. It is probable that a small 

 coagulum is first formed, from which the corpuscles are 

 washed away by the current of blood; that this becomes 

 larger by further depositions, until we have large vermicular 

 masses of fibrin, attached, in some instances, to the chordae 

 tendinese. Clots formed in this way may be distinguished from 

 those formed after death by their whitish color, dense consist- 

 ence, and the closeness with which they adhere to the walls 

 of the heart. Cases have been reported by Richardson and 

 others, where concretions of this kind extended from the 

 cavities of the heart far into the large vessels. It is also 

 stated by Richardson 1 that they sometimes become partly 

 organized, and connected with the tissue of the heart ; but 

 we have seen that accidental deposits of a proximate prin- 

 ciple, like fibrin, never become transformed into organized 

 structures. 



We need only enumerate some of the other circumstances 

 under which the blood coagulates in the vessels, as this sub- 

 ject belongs rather to pathology than to physiology. Coag- 

 ulation may be said, in general terms, to occur as a con- 

 dition of stasis. When a ligature is applied to an artery, 

 the vessel becomes filled with a coagulum up to the site of 

 the first branch which is given off, whatever be its situation. 

 In applying the ligature, the delicate inner coat is ruptured, 

 and the shreds, which curl up in the interior of the vessel, 

 soon become covered with a layer of coagulated blood, which 

 thickens until the whole vessel is filled. In cases in which 

 the flow of blood becomes arrested, or very much retarded, 

 as in varicose veins of the extremities, the enlarged veins in 

 hemorrhoids, etc., these vessels may become obliterated by the 

 formation of a clot, In some aneurisms, the retardation of 

 the blood-current produces spontaneous cure by the deposi- 

 tion of successive layers of fibrin next the walls of the dilated 

 vessel. A knowledge of this fact has been made use of in 

 the treatment of aneurism by compression of the artery which 



1 Op. tit. 



