CIRCULATORY SYSTEM. 171 



darker until it becomes a black or dark purple. This is the 

 natural or healthy aspect of horses' blood : but, human blood is 

 said never to put on such an appearance but as symptomatic of 

 inflammatory, or, at all events, of increased vascular action. 

 Whether it does or not, the simple explanation of this phenomenon 

 is, that, in consequence of the blood taking an unusually long 

 time to coagulate, the red particles, being specifically heavier 

 than the fluid containing them, gradually subside to the bottom 

 until they are arrested by the process of coagulation. And con- 

 sequently, as the horse's blood takes so much longer to coagulate 

 than the human, it cannot afford any matter Jor surprise that his 

 blood should be always buffy. Still, obvious and easily account- 

 able for as this fact is, buffy blood has been attributed to the 

 horse as a mark of disease. 



And so, in like manner, has cupped blood ; — by which is meant, 

 crassamentum, whose upper surface, instead of being flat or per- 

 fectly plane, is concave or cupped, having its surrounding margin 

 elevated and more or less inverted, in the form of a tea-saucer. 

 But this is an appearance often to be met with in perfect health : 

 one that no more certainly indicates any morbid condition with 

 which I am acquainted than does buffy blood. I had a re- 

 markable instance of this while engaged in some experiments 

 connected with this subject. A horse, to every appearance in 

 perfect health, was bled to one pound ; after which he was gal- 

 loped (for the space of about twenty minutes) until he sweated 

 profusely : while under extreme agitation from the exertions 

 he had been put to, another pint of blood was drawn by un- 

 pinning the same orifice. The coagulum of the first parcel of 

 blood was sizy, tough, contracted, and deeply cupped ; that of 

 the last exhibited no signs whatever of buff', was extremely loose 

 and flabby in its texture ; so that, on being handled, it readily 

 mingled with the serum, and in a much shorter time than the first 

 went into the putrefactive state. 



This latter fact is intimately connected with what I have 

 already advanced regarding the non-coagulation of the blood 

 after an animal has been coursed to death ; since, had exertion 

 been continued until the horse sunk under it, the blood would 

 probably have remained wholly fluid ; whereas in this case, the 

 animal being only in progress towards that state — being only 

 urged to a point from which he could recover — the coagulating 

 powers of the blood were merely diminished. 



I shall conclude this subject with a statement of the results of 

 bleeding twelve horses in perfect health, under circumstances as 

 nearly as possible similar and natural. From each horse the 

 quantity drawn was one pint. The time it took in flowing in no 



