Respiratory Functions of Body Fhiids 



311 



similar in shape.-'' '•'•'' In a duck and pigeon the difference between the oxygen 

 in arterial and venous blood shows a utilization of 60 per cent, compared with 

 27 per cent in man. In the turtle""* 44 per cent and in the skate Raja^^' 66 per 

 cent of the oxygen is removed through the circulation. In a general way 

 animals which make quick active movements (mouse, cat) have higher ten- 

 sions of saturation and half-saturation with oxygen than animals which are 

 slow and steady (dog). Also most cold-blooded aquatic animals have dissocia- 



20 



le 



16 



12 



O 



^ 10 



_J 

 O 



> 8 



20 



30 



50 



60 70 

 PP ^2 



80 



Fig. 68. Oxygen dissociation curves in volumes per cent of oxygen combined as a 

 function of partial pressure of oxygen in mm. Hg. (1) Arenicola 20°, pH 4.9; (2) 

 mackerel 20°, 1 mm. CO,; (3) man 38°, pH 7.4; (4) pigeon 42°, 40 mm. CO2; (5) 

 Amphiuma 20°, 43 mm. CO.; (6) ray 10.4°, pH 7.8; (7) Sipunculus 19°, pH 7.7; (8) 

 Cancer 23°, 1 mm. CO.; (9) Spirographis 20°, pH 7.7. Data assembled by Florkin,™ 

 except data lor Spirographis from Fox."^' 



tion curves to the left of the curves of warm-blooded animals; that is, the 

 affinity for oxygen of the hemoglobin of aquatic animals is greater. 



Effect of Carbon Dioxide. When carbon dioxide is added to mammalian 

 blood, as it is in the capillaries, the affinity of the hemoglobin for oxygen is 

 reduced and the dissociation curve moves to the right (the Bohr effect). At 

 high CO2 tensions, therefore, the oxygen tension at which hemoglobin becomes 

 saturated with oxygen is higher than it is at low COo tensions. In the tissues 



