COMPOSITION OF PLASMA AND SERUM. 51 



dog), hippuric acid, succinic acid, and uric acid (more abundant in gouty 

 conditions), hypoxanthin, all occur in very small amounts. 



The plasma and serum contain a yellow pigment, or perhaps several 

 pigments. One of these is called cholepyrrhin (horse, calf), and is 

 identical with the bile pigment of the same name (Hammafsten). 

 [Rabbit's serum is colourless.] Thudichum regards the yellow pigment 

 as lutein ; Maly, as hydrobilirubin; and MacMunn as choletelin. 



V. Sarcolactic Acid and Indican, also in small amount. 



VI. Salts. The amount of inorganic salts ('085 to "09 per cent.) 

 contained in the serum is slightly less than in the plasma, as a small 

 amount of lime and magnesic phosphate is removed by the fibrin 

 (Briicke). The most abundant salt is sodium chlwide (0*5 per cent.), 

 and next to it sodium carbonate [which exists in the plasma, most 

 probably in the condition of sodium hydric carbonate (NaHC0 3 ). 

 There is a small amount of potassic chloride, and also sulphuric and 

 phosphoric acids, lime and magnesia. It is most important to note 

 that the soda salts are far more abundant in the serum than the 

 potassium salts. The ratio may be as high as 10:1.] 



Salts in human blood-serum (Hoppe-Seyler). 



Sodic Chloride, .... 4'92 per 1000. 



Sulphate, . . . . 0*44 



,, Carbonate, .... 0'21 ,, 



Phosphate, .... 0'15 ,, 



Calcic Phosphate, ..... \ A . 7 o 



Magnesic ,, / 



VII. Water about 90 per cent. 



33. The Gases of the Blood. 



Absorption of Gases by Solid Bodies and by Fluids. 



Absorption by Solid Bodies. ~A considerable attraction exists between the 

 particles of solid porous bodies and gaseous substances, so that gases are attracted 

 and condensed within the pores of solid bodies i.e., the gases are absorbed. 

 Thus, one volume of boxwood charcoal (at 12C. and ordinary barometric pressure) 

 absorbs 35 volumes C0 2 9*4 vol. 7 '5 vol. N 1'75 vol. H. Heat is always 

 formed when gases are absorbed, and the amount of heat evolved bears a relation 

 to the energy with which the absorption takes place. Non-porous bodies are 

 similarly invested by a layer of condensed gases on their surface. 



By Fluids. Fluids can also absorb gases. A known quantity of fluid at 

 different pressures always absorbs the same volume of gas. Whether the pressure 

 be great or small, the volume of the gas absorbed is equally great (W. Henry). 

 But according to Boyle and Mariotte's law (1679), when the pressure within the 

 same volume of gas is increased, the volume varies inversely as the pressure. 



Hence it follows that, with varying pressure, the volume of gas absorbed remains 



