CIRCULATING SYSTEM. 



merits of DARWIN, already alluded to, demonstrate, that 

 there is no air in the blood while confined in the proper 

 vessels, and render it probable that the air which appears, 

 when the blood is placed under the exhausted receiver of an 

 air-pump, has been mixed with the blood upon leaving the 

 vessels and passing through the atmosphere *. 



Chemical Constitution. The serum from which the clot 

 has been removed, is more fluid than the blood itself, but 

 retains its taste and smell. It is slightly alkaline, and con- 

 sequently renders vegetable blues green. When heated to 

 the temperature of about 160, it coagulates, and if this coa- 

 gulum be cut into thin slices, a fluid oozes out, which is term- 

 ed Serosity. The coagulum has all the properties of coa- 

 gulated albumen. The serosity still contains a considerable 

 portion of albumen, whose properties are much modified by 

 the salts with which it is combined. The following are the 

 contents of the serum, as stated by different chemists : 



MARCET. BERZELIUS. 



Water, - - 900.0 905.0 



Albumen, 86.8 80.0 



Muriate of potash and soda, - - 6.6 6.0 

 Subcarbonate of soda, ... 1.65 

 Sulphate of potash, 0.35 

 Earthy phosphate, 0.60 



Lactate of soda united with animal matter, 4.0 



Soda, phosphate of soda, and a little animal matter, 4.1 



* The following, among many of his experiments, may be quoted : 

 " A part of the jugular vein of a sheep, with the blood in it, was included 

 between two strict ligatures, during the animal's being alive ; and, being cut 

 out with the ligatures, was immediately put into a glass of warm water, and 

 placed in the receiver of an air-pump. It sunk to the bottom of the water, and 

 would not rise when the air was diligently exhausted. It was then wiped 

 dry, and laid on the brass floor of the receiver, and the air again exhausted ; 

 but there was not the least visible expansion of the vein, or its contents." 

 Phil. Trans. 1774, p. 345. Similar experiments, with the same results, 

 were repeated on the blood in the vena cava inferior of a large swine. 



