328 THE BLOOD. 



The predominating solid substance in the blood is the oxyhaemo- 

 globin ; 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. The 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, 

 they are present as chlorides, phosphates, carbonates, and to a slight 

 extent also as fluorides. Some of these occur in the blood as such, 

 while others form more or less intimate combinations with the albu- 

 mins. The iron largely occurs as an integral constituent of the 

 haemoglobin molecule, of which it forms from 0.39 to 0.47 per cent. 

 Traces are also present in certain leucocytes, and notably those of 

 the oxyphilic variety. In the plasma itself it is at times met 

 with in infinitesimally small amounts, and is then referable to the 

 destruction of leucocytes. 



In addition to these constituents of the normal blood, we further 

 meet with certain gases, viz., oxygen, carbon dioxide, and nitrogen. 

 Of these, oxygen and carbon dioxide occur partly in solution and 

 partly in combination with hemoglobin, while nitrogen is found 

 only in solution. The carbon dioxide, moreover, is in part present 

 as a soluble bicarbonate, and to a certain extent also in combina- 

 tion with the albumins of the plasma. These gases may be ex- 

 tracted from the blood in their entirety by exposure to a vacuum. As 

 the nitrogen is simply held in solution, its volume is constant, and 

 corresponds to 2 per cent, by volume no matter whether the blood 

 is obtained from an artery or a vein. The relative amount of oxy- 

 gen and carbon dioxide, on the other hand, is subject to great varia- 

 tions. From the arterial blood of dogs it is thus possible to obtain 

 21 per cent, of oxygen by volume, and 38 per cent, of carbon di- 

 oxide, while venous blood contains as much as 46 per cent, of carbon 

 dioxide and only 12 per cent, of oxygen. 



As these gases can be obtained by exposure to a vacuum, it follows 

 that their combination with oxyhsemoglobin cannot be very strong ; 

 it is surprising, however, to note that in this manner not only that 

 portion of the carbon dioxide is obtained which is in combination 

 with albuminous material, but also the carbon dioxide of the car- 

 bonates. This phenomenon is owing to the fact that in conse- 

 quence of the vacuum the red corpuscles are broken down, and 

 that the haemoglobin which is thus set free is then capable of exer- 

 cising its acid properties, and causes decomposition of the salts. 



