CHANGES IN THE BLOOD. 81 



modified by disease. The blood of the horse, for example, 

 coagulates more slowly than the blood of other animals and of 

 man ; hence what is termed the buffy coat is observable in 

 coagulated healthy horse's blood, the buffy appearance on the 

 top of the clot being ascribable generally to the fact that slow 

 coagulation gives time to the blood globules, which are of higher 

 specific gravity than the liquor sanguinis, to sink towards the 

 bottom of the vessel before being incarcerated in the meshes of 

 the coagulating fibrin. To prove this, fill two vials with the 

 blood of a healthy horse, and to the blood in one add a small 

 quantity of tlie chlorate of potash, and leave the other to coagu- 

 late naturally. In the course of a very short time the blood to 

 which the chlorate has been added will be found firmly coagu- 

 lated, and with but a slight or without any buffy coat ; whilst 

 the blood to which no addition has been made remains fluid for 

 a much longer time, the globules falling to the lower parts, 

 leaving the upper portion of the clot a straw colour. 



During the first stage of coagulation, which is termed that of 

 gelatinisation, the clot appears as a semi-solid mass. In the 

 course of some time, however, it divides into serimi and clot 

 (crassamentum), the serum being pressed out by the fibrin. 

 This shows that the fibrin possesses the power of contraction ; 

 and to the presence or absence of this power the further changes 

 in the clot are due. The clot may be defective in solidity — 

 gelatinous — or it may present an excess not only of fibrin, but 

 of contracting properties. The shrunk, contracted, or cupped 

 appearance of the clot indicates increased contractility and 

 a sthenic state of the system generally ; whereas the gelatinous 

 clot is indicative of an aplastic condition of the blood and an 

 asthenic state of the system. 



