commenced. On one occasion, my glass tube broke; and the difficulties were so many, that I gave up the inquiry for the time. In the beginning of 1856, Mr. Wentworth Scott (whose kind assistance I have already acknowledged) suggested to me the propriety of placing blood under pressure, and devised for me a mercurial tube of a very ingenious kind. I tried Mr. Scott's plan with partial success, using first his tube, and then modifying it in various ways. The principle suggested was that of having a long barometer tube, bending slightly upwards at its lower part, and having the small arm removable, so that it could be filled with blood under mercury, and adapted to the long arm; the long arm itself being afterwards filled to the extent of thirtytwo inches with mercury. My ultimate modification of this apparatus is illustrated in the opposite sketch.

It consisted, as will be seen, of a central graduated long tube, connected by a curve with a shorter tube on each side at its lower part; the tubes being all continuous. The short tube on the left was closed; the long central tube open; and the right-hand one open. A piece of elastic catheter was attached to a syringe by one end, and the other end was carried to the upper part of the left-hand small arm, as delineated. When these arrangements were finished, the two short tubes, and the long tube to the height of the short ones, were filled with mercury. Blood freshly drawn was then poured into the syringe from above, the piston being removed next, the piston being replaced, the charge of blood was driven into the upper part of the left-hand closed tube, the displaced mercury flowing over from the open right-hand tube into a basin placed beneath. The blood being introduced, the elastic tube was with

drawn, a firm screw stopper was placed on the righthand tube, and the long tube was filled up with mercury to thirty-two inches.

EXPERIMENT CLXI. Blood under Mercurial Pressure. I subjected some freshly drawn lamb's blood to the operation described above, and set it aside at a temperature of 60° Fahr. I found the experiment very difficult and complicated. With the elastic tube passing through the mercury, I could not prevent the admission of some air; while the column of air in the tube forced its way before the blood. When, therefore, the blood was

introduced, the stopper put on, and the long column filled with mercury, there were in the left-hand tube three strata; one of air, superiorly; another of blood; and a third of mercury. However, two hours afterwards, on examining the tube, and displacing a little of the mercury, I found the blood quite fluid: but, in the act of displacing the mercury, I removed the pressure, and coagulation succeeded in a few minutes. In the course of an hour, the blood had separated into clot and serum. The blood of the animal used in this experiment coagulated naturally in two minutes.

To carry out this experiment to its full illustration, several conditions would be required, which are very difficult, if not impracticable. First, the blood ought to be so received under the mercury, that no portion whatever of air should be admitted with it. Secondly, the blood ought to be conveyed directly from a vessel of the living animal, without any exposure to air in its progress. Thirdly, the barometer tubing should be so perfectly smooth within, that currents of gas should not by any possibility pass between the tube and the mercury. Could these conditions be realised, the inference is clear that the experiment would succeed as perfectly in keeping blood fluid, as in the case where the blood was entrapped in a vein and then drawn under mercurial pressure. The last experiment, in which blood was kept fluid two hours, affords a complete illustration of the truth of this inference.

A simpler mode of illustrating the effects above described afterwards suggested itself. Taking advantage of the fact that cold retards coagulation, I received blood from the throat of an ox into ice, then transferred it into a bottle sold in the shops under the name

of Turnbull's eye-glass, and depicted below. The bottle was first half filled with mercury, and immersed partly

in a mixture of ice and salt, in which a thermometer stood at 17° Fahr. The remaining part of the bottle was then filled with the chilled blood. The stopper was inserted; and the little cup which surrounds the stopper was filled with mercury, the stopper being secured firmly with a twist of wire.

Blood

EXPERIMENT CLXII. subjected to Cold and Pressure. I received from the neck of an ox an ounce of blood into an ice-cup. I transferred some of this instantly to the bottle which had been half filled with mercury, so as to fill up the bottle with the blood. Next I inserted the stopper, bound it down with a twist of wire, and filled the upper cup with mercury. Lastly, I removed the bottle from the freezing mixture, and placed it in another mixture, in which the thermometer stood at 32° Fahr. Here I left it for one hour. Then, pouring off the mercury in the upper cup, and removing the stopper, I poured out the contents of the bottle into a wine-glass. The blood lay on the upper surface of the mercury in the glass completely fluid. The temperature of the air was 60° Fahr. Exposed to this, the blood coagulated, in a dark but firm clot, in four minutes and a half. The blood of the animal used in this experiment coagulated naturally in three minutes.

EXPERIMENT CLXIII. Blood subjected to Cold and Pres

sure.

I subjected the blood of another ox to the same experiment, taking exactly the same precaution, but

allowing five hours and a half to elapse before removing it from the bottle. The blood was in two conditions; part of it was fluid; the other part was in a soft gritty-like state, as though slightly frozen. When poured into a wine-glass, and exposed to the air at 60° Fahr., it all became fluid, but coagulated afterwards in a feeble clot, with a slight fibrinous separation on the upper surface. The clot ultimately remained loose and feeble. The blood of the animal coagulated naturally, on exposure to the air at a temperature of 65° Fahr., in two minutes and a half.

While this sheet was in press, I constructed a simple tubular instrument, as follows. I took a piece of barometer tubing, of half-inch bore, closed it at one end, and then bent it into the form represented in the drawing. The lower and closed part was bent upwards at an angle of 45°; the upper part terminated in a wide funnel mouth. Through the tube a long gutta percha tube, one-eighth of an inch in diameter, was carried down to the beginning of the upward bend. The gutta percha tube ended superiorly in a small funnel.

EXPERIMENT CLXIV. Blood subjected to Cold and Pressure. I received from the neck of an ox a few