Chap, vi.] OF LIVING LIQUIDS. 61 



are well known. In these fierfected organisms the blood is a 

 liquid slightly viscous, of a purple red in the arteries ; that is to 

 say, when it is freshly impregnated with aerian oxygen, but of a 

 blackish tint, more or less deep in the veins ; that is to say, 

 when from contact with the tissues it has exchanged its oxygen 

 for carbonic acid. It is well known that the temperature of 

 these two bloods differs, that of the venous blood being a little 

 more elevated in the right ventricle of the heart and in the 

 deeper veins — an elevation which we must evidently attribute to 

 the chemical reactions of nutrition, the residua of which the 

 venous blood collects. 



It is also known that the blood, as soon as it is drawn from 

 the vessels, separates into two parts — a red coagulum containing 

 the globules, and a liquid part of a lemon yellow, which is called 

 serum. 



The blood, we have said, is a medium from which all the 

 anatomical elements of the organism derive the materials needful 

 to their life, and into which they pour all their nutritive residua ; 

 its chemical composition must therefore be veiy complex. We 

 find therein in effect immediate principles of the three classes, and 

 we find therein in great number. We must content ourselves, 

 therefore, with signalising the chief of them. 



The principles of the first class, wholly mineral, are first of 

 all water, which quantitatively is the most important element, 

 as, moreover, the figure for the density of the blood shows, which 

 on an average is only 1,050. In quantity, water in man repre- 

 sents from 905 to 910 thousandths of the blood. The proportion, 

 however, notably varies ; it is more considerable in the infant, 

 the young man, the pregnant woman ; in short, wherever the 

 formation of new anatomical elements necessitates the fixation 

 of many solid materials. In this liquid mass all the other 

 immediate principles are dissolved, and the globules travel along. 



The immediate gaseous principles of the first class are oxygen, 

 azote, and hydrogen. The first of these gases, which is by far 

 the most important, comes from the exterior air from which it ia 



