VOL. tXIV.] PHILOSOPHICAL TRANSACTIONS. 537 



lo In January 1773, by the assistance of Mr. Webster, an ingenious surgeon 

 from Montrose, the above experiments were repeated in the following manner. 

 A part of the vena cava inferior of a large swine, which was killed by some 

 strokes on his head with an axe, was intercepted, when full of blood, between 

 2 ligatures. The part was about 1-i- inch long, and held, by conjecture, near 

 an ounce of blood; this was immersed in warm water as soon as it was cut out 

 of the warm body, and immediately put into the receiver of an air-pump. The 

 air was well exhausted, and again let into the receiver repeatedly, without any 

 appearance of enlargement of the vein ; which must have been easily perceivable 

 by its ascending in the warm water. The same experiment was tried on the 

 urinary bladder, with the same success, the urethra being tied with a ligature, 

 while it was still in the body. The gall-bladder rose in the warm water, though 

 the bile duct was tied before it was taken out of the body, and had air bubbles 

 appearing on its sides, like globules of quicksilver, as happened to the urinary 

 bladder in the experiments at Shiffhall ; which, in both cases, was ascribed to 

 some portion of cellular membrane adhering to the bladders, into the cells of 

 which, at the time of cutting them out, some air had insinuated itself. 'iK| 



In these experiments the water, in which the animal parts were immersed, 

 was warmed to about 100 degrees of Fahrenheit's scale, lest a greater degree of 

 heat in the water might have raised an elastic vapour from these fluids, which did 

 not naturally exist in the living animal ; and all the parts were well cleared from 

 the cellular membrane and fat ; as it was imagined the atmospheric air might in- 

 trude itself into the cellular membrane, as is seen in tearing off the skin of 

 animals recently killed, and which did indeed disappoint 2 of the above experi- 

 ments, as was manifest from the silvery globules, which appeared on the surfaces 

 of the bladders. 



From the facts established by these experiments, Dr. D. thinks the following 

 conclusions may be drawn. 1 . That so great a change is produced in the blood, 

 by its receiving, in its passage from the arm of the patient to the basin, a great 

 admixture of atmospheric air, that the experiments afterwards made on its sen- 

 sible or chemical properties are rendered very uncertain and erroneous; since the 

 florid colour of the blood, its property of coagulation, and perhaps of putrefac- 

 tion, may depend on this adscititious admixture of atmospheric air, and, at the 

 same time, we see why so much less froth is produced in the operation of cupping, 

 than from blood placed in the exhausted receiver of an air-pump; though perhaps 

 as great a degree of vacuum is made in one case as in the other. 



2. It is probable, from these facts, that animal bodies can bear much greater 

 variations of the pressure of the atmosphere, than the natural ones, without any 

 degree of inconvenience. ^ Some who have ascended high mountains are said to 

 have been seized with a spitting of blood; but as this never happens to animals 



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