3 o6 



RESPIRATION 



Combining Power of Hemoglobin with Oxygen. One hundred 

 cubic centimeters of blood contain about 14 grams of hemoglobin, page 

 137. Each gram of hemoglobin, when fully saturated with oxygen, accord- 

 ing to Hiifner's earlier determination, combines with 1.56 cc. of oxygen. 

 By later work he gets the determination of 1.34 cc. for hemoglobin of ox 

 blood. This last figure indicates that the combining power of the hemo- 

 globin is dependent upon the iron in the molecule, in which one atom of iron 

 combines with one atom of oxygen. A number of investigators have 



too 



80 



70 



50 



40 



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20 



10 



10 



20 



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5<T 



60 



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100 



FIG. 239. Dissociation curves of oxy hemoglobin in: I, 0.7 per cent, sodium chlor- 

 ide; II, in sodium bicarbonate, and III, in disodium phosphate. The figures along the 

 ordinates represent percentages of saturation of hemoglobin by oxygen. The figures 

 along the abscissae represent mm. of oxygen pressure in mercury. (Barcroft and Camis.) 



examined the conditions under which hemoglobin combines with oxygen 

 Hiifner, Bohr, Lowy, and Barcroft and Camis. Hiifner, working with 

 purified hemoglobin in watery solution, found that when the oxygen ten- 

 sion in the air in contact with the hemoglobin was increased above zero by 

 graded stages, the amount of oxygen that was combined was very great per 

 unit of increased pressure at the low pressures, but relatively less at the 



