at twenty seconds. When the beaker beneath the quarter-inch tube was full of blood, the blood it contained was perfectly fluid, and was thus returned to the reservoir. At the end of forty seconds, the currents through the eighth of an inch and quarter-inch tubes stopped flowing from coagulation, the smaller of the two stopping first by the matter of a few seconds.

EXPERIMENT CXXXVI. Transmission of Blood through Tubes of different Diameters. I experimented in a similar way to that recorded in the last experiment, on the blood of another sheep. The results were the same, with the one exception that a continuous current was not set up from the smaller tube. As the first portion of blood escaped from this tube, a bead of coagulum was formed at the mouth and sealed it up completely.

EXPERIMENT CXXXVII. Transmission of Blood through Tubes of different Diameters. I received a charge of blood from the neck of a sheep, and at once transferred it to the large cylinder or reservoir. I kept up the supply in the reservoir by the addition of a new charge of blood from the animal, an assistant keeping watch on the currents from the tubes. The flow from the smallest tube was only a few drops, and ceased from coagulation within five seconds. The flow from the second smallest tube ceased next in order, and quickly; while the currents in the two larger tubes were continuous for one minute, and stopped nearly at the same time, from the tubes becoming blocked up with red clot.

EXPERIMENT CXXXVIII. Exposure of Blood to the Air in a Stream. I caught in a spouted jug a pint of blood from the neck of a sheep. One half of this was decanted into a beaker. The other half I poured in a slow

stream from the jug into a another similar jug, repeating the process. In twenty-five seconds I felt a clot passing from one vessel to the other. At the end of fifty seconds, an assistant noted that the blood left at rest was coagulated. On examining the blood which had been poured out, I found that the mode of coagulation had been by simple separation of the fibrin, as obtains when blood is whipped with the hand. The separation of fibrin in this experiment was very perfect, as no coagulation whatever occurred when the fibrous mesh was removed from the fluid.

On the Effects of driving currents of Air through newly drawn Blood. The abstraction of air favours and hastens coagulation. The force of brisk currents of air through blood has precisely the same influence. I use the word air in this place, not because air only is implied, but because air was the compound gas usually employed in these inquiries, as being at once the readiest to hand and cheapest. The effects, however, are precisely the same, whether oxygen be the gas driven through, or nitrogen, or certain other gases, which I shall refer to further on, and which are negative in their chemical action on the blood when driven through it, but exert the ordinary physical effect of carrying with them other free gases with which they may come in contact in their course.

To be able to drive air through blood with equality of diffusion and freely, I constructed an apparatus, as shewn in the next drawing. It was simply a straight glass vessel, three inches in diameter, and eight inches in height; it was open at the top. A little below the middle part of this vessel was placed a circular tube, perforated with holes above, like a circular gas-burner;

from this a tube ascended, which, bending over the vessel, was connected with a pair of small bellows at its extreme end.

A

EXPERIMENT CXXXIX. Air driven through Blood. I received from the neck of a sheep as much blood as would fill the glass vessel above named. As soon as the vessel was filled, an assistant, who held the bellows, drove through the blood a brisk current of air. A separate portion of blood from the same animal was received in a cup, and left at rest exposed to air, for comparison. I took the periods of coagulation myself. The blood through which the air was passing was well coagulated in forty-five seconds. I now drew out the clot above the circular jet; it was a well made but spongy mass. The blood in the lower part of the glass, i. e. beneath the jets, was next turned out, and found half in clot, the rest quite fluid. The fluid part coagu

lated in one minute after removal.

The blood left

naturally at rest in the air did not coagulate for one It then set into a firm clot.

minute and a half.

EXPERIMENT CXL. Air driven through Blood. I filled the glass vessel used in the last experiment with blood from the neck of another sheep, setting a little more blood aside, and at rest in a cup, for comparison. The results were the same: the blood through which the air had passed had coagulated in a general but spongy clot in forty seconds. The blood left at rest was fluid at the end of one minute and twenty seconds, but in ten seconds more had become a firm coagulum.

EXPERIMENT CXLI. Air driven through Blood. Two equal portions of ox's blood were freshly drawn, and were received at the same time into two bottles of the same size and shape; both were open at the top. The blood in one bottle was left at rest in the air. Through the blood in the other bottle a brisk current of air was driven, by means of a tube carried to the bottom of the blood, as in the common Wolf's bottle, and connected at its opposite end with the bellows. The blood thus treated coagulated in forty seconds. The blood at rest did not coagulate for two minutes, but it formed a less spongy coagulum.

On the Exclusion of Blood from Air, and the results in regard to Coagulation. In the preceding experiments it has been shewn, that the free exposure of blood to air, as well as the removal of atmospheric pressure, favour coagulation. In the ensuing series, the effects of simple exclusion from air and of increased pressure will be demonstrated. Some of these experiments are modifications or imitations from Hewson, others are original.

[EXPERIMENT CXLII. Blood inclosed in a Tube. I took four pieces of glass tubing, two inches in length, and a quarter of an inch in diameter. I connected these tubes firmly with each other by pieces of vulcanised India rubber tubing of the same diameter. The tube thus formed was fitted with a stop-cock at each end. A current of blood fresh from the neck of an ox was now poured briskly through the tube, as shewn in the next illustration.

When the stream was full, both ends of

the tube were simultaneously closed by a turn of the stop-cocks, and a ligature was passed round the India rubber tubing between each piece of glass tube, in order that the blood inclosed in the segments might be