THE BLOOD. 89 



cles which are specially active, viz., those which work the rasp-like 

 tongue. 



B. The Carbon Dioxide Gas in the Blood. Of this gas in the 

 blood, part exists in a state of simple solution in the serum, and and the 

 rest in a state of weak chemical combination. It is believed that the 

 latter is combined with the sodium carbonate in a condition of bicar- 

 bonate. Some observers consider that part of the gas is associated with 

 the corpuscles. 



C. The Nitrogen in the Blood. The whole of the small quantity 

 of the nitrogen contained in the blood is simply dissolved in the fluid 

 plasma. 



Chemical Composition of the Blood in Bulk. Analyses of the 

 blood as a whole differ slightly, but the following table may be taken to- 

 represent the average composition : 



Water, 784 



Solids- 

 Corpuscles, 130 



Proteids (of serum), 70 



Fibrin (of clot), . , . . . . 2.2 



Fatty matters (of serum), .... 1.4 

 Inorganic salts (of serum), ... 6 



Gases, kreatin, urea and other extractive ) 6.4 

 matter, glucose and accidental substances, j 216 



' 1000 



Variations in the Composition of healthy Blood. 



The conditions which appear most to influence the composition of 

 the blood in health are these : Sex, Pregnancy, Age, and Temperament. 

 The composition of the blood is also, of course, much influenced by diet. 



1. Sex. The blood of men diifers from that of women, chiefly in 

 being of somewhat higher specific gravity, from its containing a rela- 

 tively larger quantity of red corpuscles. 



2. Pregnancy. The blood of pregnant women is rather lower than 

 the average specific gravity, from deficiency of colored corpuscles. The 

 quantity of the uncolored corpuscles, on the other hand, and of fibrin, is 

 increased. 



3. Age. The blood of the foetus is very rich in solid matter, and es- 

 pecially in colored corpuscles ; and this condition, gradually diminishing, 

 continues for some weeks after birth. The quantity of solid matter then 

 falls during childhood below the average, rises during adult life, and in 

 old age falls again. 



4. Temperament. There appears to be a relatively larger quantity 

 of solid matter, and particularly of colored corpuscles, in those of a ple- 

 thoric or sanguineous temperament. 



5. Diet. Such differences in the composition of the blood as are due 



