. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. 310 Comparative Animal Physiology variable number of iron units combining with oxygen, to the interaction be- tween groups, and in part to the effects on hemoglobin of other components of the blood such as the blood salts. Purified hemoglobin gives a more nearly hyperbolic oxygen dissociation curve than does hemoglobin in blood or in the presence of blood salts. The Oo dissociation curve of muscle hemoglobin is more nearly hyperbolic than that of blood hemoglobin, and it lies to the left of the blood curve; that
. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. 310 Comparative Animal Physiology variable number of iron units combining with oxygen, to the interaction be- tween groups, and in part to the effects on hemoglobin of other components of the blood such as the blood salts. Purified hemoglobin gives a more nearly hyperbolic oxygen dissociation curve than does hemoglobin in blood or in the presence of blood salts. The Oo dissociation curve of muscle hemoglobin is more nearly hyperbolic than that of blood hemoglobin, and it lies to the left of the blood curve; that is, myoglobin has a greater oxygen affinity than blood hemoglobin and can take oxygen from it. Dog myoglobin is only 40 per cent dissociated at 5 mm. of Oo; the blood hemoglobin is 95 per cent dissociated at this tension.'^^ Except at moments of stress, myoglobin remains saturated. The oxygen tension at which the pigment is 95 per cent or more saturated is called the loading tension (ti) or tension of saturation (tsat); the oxygen tension at which the pigment is 50 per cent saturated, that is, when Hb equals HbOo, is the unloading tension (tu) or tension of half saturation (ti/o sat)-. 30 40 50 OXYGEN PRESSURE Fig. 67. Oxygen dissociation curves in per cent saturation of hemoglobin as a function of oxygen pressure in mm. Hg in a variety of animals. Data assembled by ;^ In Table 55 the ti/o ^at and the tsat of a number of animals are compared under nearly physiological conditions. In Figure 67 are plotted oxygen dis- sociation curves of the blood of some animals (pigeon, crocodile) in which the affinity for oxygen is low, , the tj/o sat is high, and of other animals (^Arenicola and eel) which have a great affmity for oxygen, , the ti/2 sat and tsat are low. In Figure 68 similar curves are plotted, using the actual amount of oxygen combined in volumes per cent instead of per cent saturation as ordinate. From the data of Table 55 and of Figures 67 and 68, it
Size: 2143px × 1166px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookpublisher, booksubjectphysiologycomparative
