PHYSIOLOGY. 193 



is only within the period now mentioned that we have acquired 

 any distinct notions of a fundamental doctrine, or, in other 

 words, of the state of aggregation in the mass of blood. Even 

 with respect to this last, there still remains much doubt and ob- 

 scurity ; but, notwithstanding these difficulties, I shall endeav- 

 our to consider what may be said with regard to the state of the 

 fluids." M. M. 



CCXLIV. The red fluid passing from the lungs to the left 

 ventricle of the heart, and thence by the aorta and its branches 

 to every part of the body, may be considered as a mass contain- 

 ing, either formally or materially, every part of the animal 

 fluids, and may therefore be properly called the common mass 

 of blood. This term, however, must be strictly confined to the 

 circulating fluids while they retain their red colour ; for, when 

 they lose this, it is always in consequence of some separation of 

 parts. The same red fluid, indeed, as it is found in the veins, 

 has also suffered some separation of parts ; but as the blood in 

 the veins is never entirely deprived of the whole of any matter 

 that was present in the arteries, so we think the venous blood 

 may still be considered as a part of the common mass. 



CCXLV. This mass of blood we find to be an heterogene- 

 ous aggregate ; and it will be proper to inquire into the several 

 parts of this, before we employ any chemical trials for discover- 

 ing the mixture of the whole, or of its parts. 



CCXLVI. We discover the parts of this aggregate chiefly 

 by the spontaneous separation of them, which takes place upon 

 their being drawn out of the vessels of a living animaL 



CCXLVII. The separation commonly proceeds irr this man- 

 ner : immediately after the blood is drawn out, it exhales a sen- 

 sible vapour, and, after some time, it is found by that exhala- 

 tion to have lost a part of its weight, more or less, according to 

 the degree of heat it is exposed to, according to the extent of 

 surface by which it is exposed to the air, and probably also ac- 

 cording to different conditions of the blood itself. The matter 

 thus exhaling may be called the halitus or vapour of the blood. 



CCXLVI II. Soon after the blood has been drawn out of 

 the vessels it loses its fluidity, and the whole of it concretes into 

 one soft gelatinous mass ; but, after some time, there oozes out 

 from this mass a, thin fluid, and as the separation of this 

 VOL. i, N 



