Respiratory Functions of Body Fluids 



327 



The effect of CO. or of decreased pH is shown for Limidus in Figures 81 

 and 82. As the solution of hemocyanin becomes more alkaline the oxygen 

 dissociation curve shifts to the right up to pH of 8.6; at pH 9.4 the curve is 

 moved back to the left. In Limulns, Busycon, and Helix the minimum affinity 



-I I i_ 



Fig. 81. Effect oH pH on O2 tension for half saturation of blood. • Loligo, Q Homarus, 

 A Limulus. Redfield and Ingalls.'"'" 



for oxygen is in the alkaline range, whereas in Loligo, Homarus, Maja, and 

 Cancer the minimum Oo affinity is on the acid side, as it is for hemoglobin 

 (Fig. 81).!-^ In the snail Helix the affinity for oxygen is minimum at pH 7.7, 

 and the oxygen dissociation curve moves to the left on both the acid and 

 alkaline side of this pH.^- It has been suggested^^' that the increased O2 affini- 

 ty with added COo permits the hemocyanin to load with oxygen when animals 

 like Busycon and Linndus enter stagnant high-CO^ water. Certainly the 

 blood would load at a lower O^ tension in the presence of CO2 than in its 



