292 DR. DAVY'S ACCOUNT OF SOME EXPERIMENTS ON THE BLOOD. 



I shall briefly mention the trials which I consider most conclusive, and which sa- 

 tisfied me in spite of an opposite pre-existing bias. 



Vials provided with well-ground glass stoppers were filled with distilled water, de- 

 prived as much as possible of air by the air-pump ; they were then placed under the 

 receiver and kept in vacuo until all adhering air was removed ; the stoppers were now 

 introduced, all air being excluded, and they were instantly immersed in distilled water, 

 which had been well boiled. Thus prepared they were taken to an adjoining slaughter- 

 house, where they were filled with Sheep's blood in the following manner, without its 

 coming in contact with the air. For venous blood the jugular vein was exposed ; 

 two ligatures were applied to it ; the vein was divided between the two, and the upper 

 part, slightly detached, was introduced into a prepared vial under water the instant 

 the stopper was withdrawn, and laid open. The heavier blood proceeding from the 

 vessel of course expelled the water; and when it was supposed to be all expelled the 

 stopper was restored, and the vial was replaced in the water. In the instance of ar- 

 terial blood it was collected in the same manner from the carotid artery. In some 

 trials the blood was allowed to coagulate undisturbed ; in others the fibrin was de- 

 tached, and the liquidity of the blood preserved by agitating it, the instant the stopper 

 was replaced, with some mercury, introduced with the distilled water, and equally 

 deprived of adhering air. 



In about half an hour from the abstraction of the blood, in every instance, it Wcis 

 subjected to the air-pump. The instant the stopper was withdrawn the vial was 

 placed in a small receiver on the plate of the pump, and covered with a little larger 

 receiver, and the air as soon as possible exhausted. No appearance of disengagement 

 of gas was perceptible until the exhaustion was nearly complete ; then it was sudden, 

 sometimes considerable, even to overflowing, in the form of bubbles, and it continued 

 some time. The results were not distinctly different, that I could perceive, whether 

 venous or arterial blood was used ; I am disposed to think, on the whole, that less 

 air was disengaged from the arterial blood than from the venous. 



When blood allowed to coagulate in the vessels was tried, the results varied a little, 

 and appeared to me instructive. At first, on exhaustion, only a few particles of air 

 were disengaged ; no more, it might be supposed, than were derived from the contact 

 of the end of the stopper. In two experiments such was the appearance for at least 

 five minutes, conveying the idea that no air was extricated ; then abruptly a bubble 

 or film burst with some force, as was denoted by the scattering of the particles of 

 blood ; and a bubbling commenced and continued, rendering the indications of ex- 

 trication of gas unquestionable. And in conformity with this result I may remark, 

 I have never succeeded in obtaining indications of air in the blood in operating on it 

 by the air-pump, if confined in a detached portion of vein, or in the heart of animals, 

 the great vessels, previous to excision, having been tightly secured by ligature. In 

 no instance of this kind have I witnessed any distention, such as occurs if air be ad- 

 mitted previous to the application of the ligatures : clearly indicative, it appears to 



