CHEMICAL EXAMINATION OF THE BLOOD. 311 



actually the case ; but as the waste matter is rapidly eliminated, 

 representatives of this group are normally present in only very 

 small amounts. Certain food-stuffs, moreover, which are not im- 

 mediately required by the body in large quantities, such as fats and 

 carbohydrates, are likewise present only in traces. They are stored 

 in various tissues of the body until needed, but even then only 

 small quantities appear in the blood at one time. The only food- 

 stuffs, in fact, which are always present in the blood in large quan- 

 tities, are the albumins. These, however, must be sharply separated 

 into two classes, viz., into those which are normally present as 

 integral constituents of the cellular elements of the blood, and which, 

 of course, do not represent food-material, and into the so-called cir- 

 culating albumins of the plasma. In addition to these elements, we 

 also meet with mineral salts, a very large amount of water, and 

 with certain gases. 



A general idea of the chemical composition of human blood 

 may be had from the following table, which is calculated for 1000 

 parts by weight : 



Ked corpuscles l 480.00 



Water 276.90 



Oxy hemoglobin 193.90 



Stroma 2 9.12 



Plasma 520.00 



Water 477.36 



Albumins 35.88 



Extractives 2.39 



Inorganic salts 4.36 



From this analysis it will be seen that almost one-half of the 

 total weight of the blood is referable to cellular elements, and that 

 in the liquid portion proper there is not more than 8.2 per cent, 

 of solids, of which 6.9 per cent, is albumins, and 0.84 per cent, 

 mineral salts and 0.46 per cent, extractives. The predominating 

 solid substance in the blood is the oxy haemoglobin ; it represents 

 about 19 per cent, of the total weight of the blood, 40 per cent, of 

 the weight of the blood-corpuscles, and 95 per cent, of all organic 

 material present. 



The native albumins, which are found in the circulating blood, 

 are serum-albumin, serum-globulin, and fibrinogen. Xhe extractives 

 comprise traces of fats, soaps of the higher fatty acids, lecithin, 

 glucose, animal gum, glycogen, sarcolactic acid, urea, kreatin, uric 

 acid, and possibly also minimal amounts of the xanthin bases. 

 Nucleo-albumins, albumoses, and some of the lower fatty acids, oxy- 

 butyric acid, acetone, bilirubin, melanin, and other less well-known 

 bodies have further been found under pathological conditions, but 

 are not seen in normal blood. 



The mineral constituents comprise sodium, potassium, calcium, 

 magnesium, and iron. With the exception of the last mentioned, 



1 The white corpuscles, because insignificant in amount, have been ignored. 

 2 This includes mineral salts. 



