posed to the temperature of the external air at 65° Fahr. As soon as the blood had reached the exhausting cup, the stopper, with the wick ignited, was inserted. At the end of one minute I removed the stopper, and found the blood not fully coagulated. I therefore relighted the wick, and again introduced it. After forty seconds had elapsed, I once more withdrew the stopper, and removed the blood in a firm and uniform coagulum. Turning now to the blood in the cup, I found it still fluid. It coagulated thirty seconds later, the clot being firm and uniform.

EXPERIMENT CXXV. Blood under reduced Pressure. I caught an ounce of blood from the neck of a sheep. Half this blood was at once poured into the exhausting cup, and the stopper, with the wick ignited, was inserted. The remaining half of the blood was placed in an open cup, exposed to the external air, at a temperature of 65°. At the end of forty seconds I raised the stopper, and turned out the blood from the exhausting cup in a firm coagulum. At the end of one minute, the blood that had been exposed to the air coagulated loosely; and, in twenty seconds more, it had become a firm coagulum.

EXPERIMENT CXXVI. Blood under reduced Pressure. I received an ounce of blood by measure from the neck of another sheep, and poured half of it into the exhausting cup, instantly inserting the stopper with the lighted wick; the remaining half ounce of blood was left exposed to the air (temperature 65°), as before. At the end of half a minute I removed the stopper of the exhausting cup, and turned out its contained blood in a firm coagulum. Turning next to the blood exposed to the air, I found it so fluid that I could pour it in an unbroken liquid

current into another vessel. It did not begin to coagulate for fifty-five seconds, and then formed quickly into a firm clot.

EXPERIMENT CXXVII. Blood under diminished Pressure. One ounce of sheep's blood, freshly drawn, was used as before. Half an ounce was poured into the exhausting cup; and the remainder was left in the open cup, at a temperature of 65°. After forty-five seconds I removed the stopper of the exhausting cup, and turned out its contained blood in a firm clot. The blood in the open cup was still perfectly fluid, and could be poured from one vessel into another; it remained fluid thirty seconds longer. It then set into a firm clot.

It would be needless repetition to illustrate this section further, by the detailing of similar observations. There are no experiments more easy or satisfactory to perform than those with the exhausting cup. Of course a little manipulative practice is required; but this achieved, the stopper of the exhausting cup well fitted, the blood received in the first gush from the animal, and a competent assistant at hand to note and indicate time, and every experiment becomes a success; i. e. the blood in the exhausting cup may be turned out each time a coagulated mass, while the blood in the open cup is yet fluid. In some instances, the blood of the sheep coagulated so quickly on the introduction of the stopper and lighted wick, that, on removing the stopper, after counting twenty seconds, I found the blood fully coagulated. The rapidity in these cases occurred from the more perfect abstraction of the air. Indeed, if a portion of blood from the sheep could, by any possibility, be introduced suddenly into a perfect vacuum, its coagulation would, I believe, be the act almost of a

moment.

The effect of the vacuum on coagulation is nowhere better shewn than in the ordinary operation of drawing blood by cupping. In this operation, the blood which escapes into the glass coagulates with remarkable activity. I once observed blood thus extracted coagulate at the depending part of the glass in twenty seconds; whilst other blood, drawn at the same time, from a lancet puncture in a free part of the back, did not coagulate for a full minute. Indeed, the success of the operation of cupping depends upon the expedition with which a free quantity of blood can be drawn into a glass placed as lightly as is possible on the flesh. If too great a portion of air is extracted from the glass when it is applied to the skin-in other words, if too perfect a vacuum is produced-the blood coagulates immediately, and the incised wounds becoming quickly filled with clotted blood, the operation in great part fails.]

EXPERIMENT CXXVIII. Effects of drawing Blood through Pointed Tubes. I drew out six tubes, from a piece of glass tubing of the quarter-inch bore, into tapering points, as shewn in the drawing. I dipped one end of

each tube into ox's blood, freshly drawn, and then drew up from the other end by my mouth. As each tube filled, I handed it to an assistant, for the purpose of his sealing it up hermetically at both ends with the spirit-lamp and blow-pipe. To my momentary surprise (for I was not at that time prepared for such an event, and had, indeed, another object in view), the blood thus treated coagu

lated much more quickly than did some blood from the same animal, which was exposed to the air; indeed, the blood had coagulated in the tubes before their fine ends could be annealed. I learned afterwards that this rapidity of coagulation arose from my having drawn the blood into the tubes by the vacuum process. This observation led to several special experiments.

[EXPERIMENT CXXIX. Blood drawn through a Pointed Tube. I drew out a quarter-inch tube three inches long into tapering points. The opening at each extremity was the twentieth of an inch in diameter. I caught a little blood from the neck of an ox in a cup, immersed one end of the tube into the blood, and drew blood from the other end very slowly through it with my mouth. As soon as the tube was filled I withdrew it from the blood; but coagulation was so far commenced that the fluid would not flow out of either end when the tube was held upright. The blood in the vessel, from which the supply to the tube was taken, did not coagulate for two minutes later.

EXPERIMENT cxxx. Blood drawn through a Pointed Tube. I drew out a quarter-inch tube to six inches long, the ends tapering: the one end was brought out to a diameter of the twentieth of an inch; the other end was drawn out to a point into which a fine sewing needle, number eight, could only be introduced. I now dipped the wider end into a little blood drawn from an ox, and drew up strongly from the finer end of the tube. I succeeded in filling the tube with blood; but on removing it, instantly, its contained blood was found firmly coagulated. The blood of this animal, exposed freely to the air, coagulated a full minute later than that in the tube.

EXPERIMENT CXXXI. Blood drawn through a Pointed

Tube. I drew out a glass tube of a quarter-inch bore into two fine ends, the diameter of each end being such as to admit only of the introduction of a fine needle, of number nine size. I immersed one end of this tube into a little blood freshly drawn from an ox, and then drew up strongly by my mouth. The blood rose at first; but I could not, with all my force, fill the tube completely. While making the suction effort, the blood coagulated, and was fixed in the tube. At that moment. the blood in the cup, exposed to the air, at a temperature of 68°, was completely fluid, and remained so two minutes longer, when it set into a firm coagulum.

EXPERIMENT CXXXII. Blood drawn through a Pointed Tube. I drew out another tube, of the same length and central diameter as the last named. One end was drawn to the needle-point diameter; the other end was drawn to the twentieth of an inch in diameter. I immersed the finer end of this tube into half an ounce of blood, that moment drawn from the neck of a lamb, and then, with my mouth at the wider end, drew up the blood gently but continuously. In ten seconds the tube was full. When full, I gently blew downwards, and drove out for a moment a thin blood stream; but the current stopped almost instantly, from coagulation having occurred at the fine end of the tube, and in ten seconds more all the blood in the tube was firmly set. The blood left in the cup, from which the tube was filled, remained perfectly fluid for a minute and a half, as it lay exposed to the air (the temperature of which was 70° Fahr.), but it had coagulated firmly at the end of two minutes.

These experiments, very simple to perform, need not be multiplied; they are, in fact, but modifications of the exhausting cup and air-pump processes. By pro