It has been roughly estimated that the blood is divided about as follows, between the different parts of the body: the heart, lungs, and large vessels holding one-fourth, the skeletal muscles one-fourth, the liver one-fourth, the remaining quarter being distributed over the balance of the body. The blood varies within wide limits in its coagulability, and this variation occurs apparently even within conditions of health. In some patients the blood may be seen to coagulate almost as rapidly as it collects upon the surface, while in others the exposed parts continue to ooze, and the checking of hemorrhage is a difficult, sometimes almost impossible, matter. There are certain diseases in which the blood is known to have reduced power in this direction; for example, in the toxemias, especially those connected with biliary obstruction and jaundice. There were not a few of these cases of slow bleeding to death in days gone by, simply because the capillary hemorrhage could not be controlled. Recently, it has been shown that calcium chloride administered internally has a marked effect in favoring coagulation, and when opportunity is afforded it should be given for several days previous to operating and as part of the necessary preparation. It may be administered in doses of from 1 to 2 Gm., and should be given three or four times, at least, in twenty-four hours. A test of the coagulation time, normally three to five minutes, but lengthened under circumstances like those mentioned above, even to an hour, will often prove of great value. There are certain albumoses whose effect on coagulation of the blood is very suggestive and very mysterious. A very minute dose of cobra poison, for instance, will make the blood of an experimental animal remain fluid for days, unless this animal has been previously immunized against it, in which case coagulation takes place even more rapidly than normally. A trace of serum from an immunized rabbit is enough to prevent the fluidifying effect of the cobra poison, but quite insufficient to neutralize its toxic effects. The surgeon practically never desires to reduce coagulability of the blood, but frequently to increase it. When it is increased by natural conditions or those not easily controlled, then it may lead to thrombosis and produce trouble in that way.