Res-piratory Functions of Body Fluids 



329 



ports much of the oxygen. Direct measurements of oxygen tension and Hey 

 saturation in blood entering and leaving the gills in Limidiis, Hoviarus and 

 others would settle the question of whether Hey functions in these animals as 

 an oxygen carrier. 



A rise in temperature moxes the oxygen dissociation curve to the right in 

 those hemocyanins in which it has been examined'-' (Fig. 83). 



It must be concluded that convincing evidence that hemocyanin functions 

 in oxygen transport is available only for the cephalopod molluscs and Biisycon. 

 However, measurements of per cent saturation of hemocyanin entering and 

 leaving the gills of Limidtis and of similar animals have not been made. 



CARBON DIOXIDE TRANSPORT 



CO^, Dissociation Curve. Just as with oxygen, the amount of carbon dioxide 

 contained in body fluids greatly exceeds the amount in solution. The solubility 



20 30 40 

 CO2 TENSION 



Fig. 84. Carbon dioxide dissociation curves. Volumes per cent of CO:; as a function of 

 COj tension in mm. Hg. Data assembled by Redfield.^"' 



of CO2 in human blood is 48 volumes per cent at 760 mm. pressure and 37.5°, 

 the CO2 tension in alveolar air is 40 mm., hence the amount of COo which 

 might be dissolved in the blood is 2.5 volumes per cent. Actually arterial blood 

 contains 45-50 volumes per cent. Similarly, sea water has a solubility coeffi- 

 cient at 24° of 0.71 volumes per cent of CO;, and in equilibrium with air where 

 the CO2 partial pressure is 0.23 mm. Hg it would dissolve 0.0215 volumes per 

 cent; normally sea water contains about 4.8 volumes per cent of COo. The 

 difference between the COo dissolved and the COo actually contained is 

 due to the combination, largely as bicarbonate with cations, from various 



