clot. Its coagulatory force after this was not further developed.

Blood under Oil. An experiment of receiving blood under oil was performed some years since by Dr. Babington. He immersed the head of a cock under oil, and in this position cut off the head and allowed the blood to sink to the bottom of the vessel. In these experiments Dr. Babington observed, as he informs me, a retardation in the process of coagulation, and in some instances the formation of a slight buffy coat.

Modifying Dr. Babington's process in some particulars, I went through a series of like experiments, the results of which were so uniform that one might be taken as the type of all. I shall give, however, examples to illustrate the modifications in the method of experiment.

EXPERIMENT CLVIII. Coagulation under Oil. I filled a tube eighteen inches long and one inch and a half in diameter, with sperm oil. A narrower but longer tube, with a funnel top, was carried to the bottom of the oil. One ounce of blood, that moment drawn from the neck of a sheep, was at once deposited beneath the column of oil through the smaller tube, which was then slowly withdrawn. An evolution of gaseous matter took place from the blood. After three minutes had passed, I found, by gently agitating the fluids, that the blood was liquid. Three minutes later still, from the solidity of the under stratum of blood, it was clear that coagulation had occurred. The oil and blood, in the same positions, were set aside for twelve hours in a warm room. At the end of this time, on observing the two fluids, a pale film or crust was seen to lie between them. I inferred that this was a buffy coat, but on decanting the oil carefully, it turned out that the pale

P

layer pertained to the oil only. The blood beneath was a dark, soft, but tolerably uniform coagulum.

The blood of the animal used in this experiment coagulated in a firm red clot in one minute and a half.

EXPERIMENT CLIX. Coagulation under Oil. I laid bare the external jugular vein of a healthy dog. An assistant seized with forceps the vein at the upper part of the wound. Meanwhile I made an opening into the vein, and inserted in it a small metal tube, tying the tube firmly in its place. Continuous with the metal tube was a small elastic tube, six inches in length. When all was complete, the free end of the elastic tube was immersed under oil, which was confined in a glass test-tube eighteen inches long and half an inch in diameter. The forceps were next removed from the vein, and a current of blood at once gushed into the oil. The elastic tube was then withdrawn; about half an ounce of blood having been thus caught under the oil. The blood sank very gradually to the bottom, giving off bubbles of gas, which rose freely in the oil. By gentle motion of the tube I was able to note that the blood under the oil had coagulated in from two and a half to three minutes. The oil and blood were set aside in the tube for twenty-four hours. Observed then, the same appearances were presented as in the previous experiment. There was a thin pale film between the blood and oil. When the oil was decanted off, the blood beneath was found free of buffy coat, dark and coagulated, but the clot was broken and very soft. A little blood of this animal, caught in a cup by my assistants, coagulated on exposure to the air, in a firm, red clot, within a few seconds of two minutes. The vein was left untied, and the animal recovered without a bad symptom.

EXPERIMENT CLX. Coagulation under Oil at a Low Temperature. I took the glass tube delineated at page 203. I filled both limbs to within two inches of the top with oil, and then immersed the lower part of the tube in a mixture of ice and salt, in which the thermometer stood at 17° Fahr. I then poured through the long funnel tube, which had been carried through one column of the oil, one ounce of freshly drawn blood from the jugular vein of an ox. Four minutes afterwards, the blood under the oil was still fluid; but a few bubbles of gas rose on each surface of blood, and formed a froth. A few large bubbles also ascended very slowly through the oil. I now removed the tube from the cold mixture, and immersed it in water at 100° Fahr. There was at once a more liberal extrication of gases; and in two minutes the blood was an uniform coagulated column. On pouring off the oil, the blood escaped from the tube modeled to it, in a firm round cord. The blood of the animal coagulated naturally, on exposure to the air, temperature 63°, in two minutes and a half.

Experiments with Cold and Pressure. In the year 1851, I conducted several inquiries as to the effect of pressure on newly drawn blood. In those experiments, I employed the screw-piston syringe, invented by my friend Dr. James Arnott. To the lower part of this syringe I fixed a strong glass tube, closed at its further end. I then filled the syringe with blood from above, the piston being removed. When the barrel was nearly full of blood, the piston was replaced; and, by a few gentle turns of the screw, pressure was applied. The experiment was unsatisfactory: much time was lost in adapting the screw, and coagulation sometimes occurred before the experiment could be considered fully

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