COMPOSITION OF THE BLOOD. 129 



ments. Their presence is indicated by the appropriate tests 

 applied to the residue of the blood after incineration, which 

 show the well-known reactions of the chlorides, sulphates, 

 phosphates, and carbonates, with sodium, potassium, lime, 

 magnesia, and iron. In addition we have certain gases 

 (oxygen, nitrogen, and carbonic acid), which maybe extracted 

 by the air-pump or by displacement. 



2. Organic, Non-nitrogenized Constituents. These are 

 the sugars and fats ; which are separated from the other ele- 

 ments without much difficulty, and may be recognized by 

 their peculiar properties. 



3. Organic, Nitrogenized Constituents. These constitute 

 the greater part of the blood, and are inseparably connected, 

 in their functions, and as a condition of existence, with the 

 inorganic principles. They may be extracted by processes 

 already described in treating of fibrin, albumen, 'and globu- 

 line, and recognized by their peculiar properties. 



Most of the constituents of the blood are found both in 

 the corpuscles and plasma. It is difficult to determine the 

 different constituents of these two parts of the blood. It has 

 been shown, however, by Schmidt, of Dorpat, that the phos- 

 phorized fats are more abundant in the globules, while the 

 fatty acids are more abundant in the plasma. The salts with 

 a potash base have been found by the same observer to exist 

 almost entirely in the corpuscles, and the soda salts are four 

 times more abundant in the plasma than in the corpuscles/ 

 All the iron exists in the red corpuscles. 



The proportions of the various constituents of the blood 

 are subject to certain variations. These points, with their 

 relations to the tissues in the processes of nutrition, have 

 been so fully taken up in the consideration of Proximate 

 Principles, that they do not demand special notice in this 



1 MILNE-EDWARDS, Lemons sur la Physiologie, etc., tome i., p. 225. 

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