386 PHYSIOLOGY. 



were mainly held in solution, then the blood would give it up in a 

 forming vacuum in direct proportion to the falling oxygen-pressure. 

 That these conditions do not follow tends to establish the fact that 

 the oxygen is held by some chemical union. Experimental physiol- 

 ogists also tell us that in their work they notice that very little 

 is given off in a forming vacuum until a very much reduced pres- 

 sure is reached, when there is a sudden evolution of the gas, just 

 as though it had been freed from some restraining influence. The 

 restraint is now generally accepted to be the chemical union before 

 mentioned. 



Physiologists admit to-day that the major portion of the oxygen 

 of the blood is contained in the red corpuscles, which are the special 

 messengers for carrying it to the different tissues. When you compare 



A. Arterial blood per 100. V. Venous blood per 100. 



33 C 14 



CO* 64 (702 83 



N 3 N _3 



100 100 



Az is nitrogen. 



Fig. 143. Relative Proportion of Gases of Blood. (LANGLOIS.) 



the same amount of blood with an equal amount of water in regard 

 to the absorption of oxygen both agitated in the air, it is found that 

 blood absorbs more. The same amount of oxygen is absorbed whether 

 you breathe air or oxygen. At a low partial pressure laked blood had a 

 relative higher saturation than unlaked blood, for oxygen. The pres- 

 sure of the C0 2 regulates the absorption of by the blood, according 

 to Bohr. When the 0-pressure is low and C0 2 -pressure high, the blood 

 has a diminished capacity for oxygen. Haldane and Smith also found 

 out that the oxygen capacity varies with the coloring power of the 

 blood. The red corpuscles contain about 40 per cent of haemoglobin. 

 This coloring material is not the same as haemoglobin in crystals for 

 their capacity to absorb oxygen is different. A 40-per-cent. solution 

 of haemoglobin in crystals cannot be made. Bohr believes that there 

 are four different varieties of haemoglobin, which combine with 



