203 



spot in the middle. They are solid, and formed by a nucleus or red 

 point, covered over by a membranous vesicle, which appears to be rea- 

 dily formed and destroyed. 



XC. The blood, wheti no longer in the course of the circulation, and 

 on being received into a vessel, parts with its caloric, and exhales, at the 

 same time, a powerful smell, a gas to which, according to some physio- 

 logists (Moscati, Rosa, &c.), it owes its vital properties, and the absence 

 of which is attended with a loss of its vitality ; so that its analysis cannot 

 furnish facts applicable to the explanation of the phenomena of health 

 and disease. This odour, extremely strong in carnivorous animals, is 

 very distinguishable in man, especially in arterial blood. I remember 

 retaining it, a whole day in my throat, after removing the dressings, and 

 suppressing a hemorrhage, occasioned by a relaxation of the ligatures, a 

 -week after the operation for popliteal aneurism. Unless by agitation it 

 is prevented from coagulating, as it cools, its consistence increases, and, 

 on being laid by, it separates into two very different parts, the one aque- 

 ous, more or less red, heavier than common water, and evidently saltish ; 

 this is called the serum, consisting of water, in which are dissolved albu- 

 men, gelatine, soda, phosphates, and muriates of soda; nitrate of potash, 

 and muriate of lime. 



Serum, though bearing some analogy to the albumen of egg, differs 

 from it, in forming on coagulating, a less solid and less homogeneous mass. 

 The albumen is evidently mixed with a portion of transparent gelatine, 

 not coagulable by heat. Albumen has so great an attraction for oxygen, 

 that it is fair to presume, that the serum absorbs oxygen and combines 

 with it, through the very thin parietes of the air cells of the lungs, and 

 that it gives to the arterial blood that spumous appearance which is one 

 of its distinguishing characters. This oxidizement, and the fixation of 

 the caloric which accompanies it, equally increase its consistence. It 

 does not, however, coagulate ; because it is kept in perpetual motion by 

 the circulatory action, and is diluted by a sufficient quantity of water; 

 because the animal temperature, which never exceeds thirty-two or thir- 

 ty-four degrees, cannot give a solid form to albumen, which coagulates 

 only at fifty degrees of Reaumur's thermometer; and lastly, because as 

 serum contains a certain quantity of uncombined soda, which enables it 

 to turn green vegetable blues, this alkali concurs in keeping the albumen 

 in a dissolved slate, which it renders fluid, when it has been coagulated 

 by the acids, by heat, or by alcohol. 



Amid the serum, and on its surface, there floats a red cake, spongy, 

 and solid, (insula rubra} which, by repeated washing, may be separated 

 into two very distinct parts. The one is the cruror or the colouring mat- 

 ter which mixes with the water; it is a more highly oxygenated and more 

 concrescible albumen than that of the serum; it holds in solution of 

 soda, as well as phosphate of iron, with an excess of iron*. 



* It is a more oxygenated and a more coagulable albumen than that of the serum. 

 The colouring part of the blood, when incinerated, after giving off a considerable quan- 

 tity of ammonia during the combustion, leaves ashes which, according- to BEHZELIUS, 

 are only a hundreth part of its weight, and which contains 56 parts of the oxide of iron, 

 8 of the phosphate of lime, a little magnesia, 17 parts of lime, and 16 of carbonic 

 acid. The oxide of iron is neither found in the ashes of the coagulable part of tae se- 

 rum, nor of those of the fibrine. BERZELITJS, however, farther informs us, that the 

 serum, although able to dissolve a small portion of the oxides of iron, but not of its 



