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 
allowed 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 buffy coat. In proportion 
to the slowness 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 
buffy 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, 
