Respiratory Functions of Body Fluids 309 



TABLE 55 (continued). RESPIRATORY CHARACTERISTICS OF BLOOD 



not usually a hyperbola as it would be if one molecule of O2 always com- 

 bined with a single hemoglobin molecule; actually the four atoms of iron in 

 hemoglobin may combine with four or with less than four molecules of oxygen. 

 The sigmoid shape of the dissociation curve (Fig. 67) is due in part to the 



