BLEEDING. 315 



moving it about induces motion in the jaws, and facilitates 

 the rapidity of the stream by the action of the muscles in 

 connexion with the vein. 



In the operation of bleeding the blood should be received 

 into a vessel the dimensions of which are exactly known, so 

 that the operator may be able to judge from time to time of 

 the quantity that has been taken. The blood ought also to 

 flow in a regular stream into the centre of the vessel ; for if 

 alloAved to trickle down the edges it will, when cold, not 

 exhibit those changes necessary for ascertaining the degree 

 of inflammation. But to those accustomed to the pulse, 

 it will form a better criterion when taken in connexion 

 with the other symptoms. "When it has been necessary to 

 repeat the bleeding, if more than three or four hours have 

 intervened, it will be better to make a fresh incision lower 

 down than to open the old wound. The blood coagulates 

 soon after it is drawn. That portion of it which is coagu- 

 lable is composed of two substances — that which gives colour 

 to the blood, and the thinner part in which the red particles 

 float. By degrees these separate, and the red particles sink 

 to the bottom. If coagulation takes place slowly, the red 

 particles have more time to sink through the fluid portion, 

 and there appears on the top a thick, adhesive, pale, yellow- 

 ish orange substance, called the bufly coat. In proportion 

 to the sloAvness of coagulation and the thickness of this 

 coat, the degree of inflammation is determined. In the 

 healthy condition, coagulation is more rapid, and conse- 

 quently the red particles have not time to sink, and the 

 bufly coat is thin. "When the horse is much exhausted, and 

 there is a general decay of his constitution, coagulation will 

 not take place at all, but the blood will exhibit a uniform 

 blackish colour, with a thin and loose consistence. When 

 blood is drawn from a large orifice, coagulation is slower 



