254 



RESPIRATION 



factor which was overlooked in the earlier observations is the 

 influence of salts. 



The form of curve (a rectangular hyperbola, Fig. 119) which Hiifner 

 put forward by an unjustifiable generalization, as the curve of dis- 

 sociation of oxyhaemoglobin is only found when the haemoglobin solu- 

 tion is thoroughly freed from salts, as by prolonged dialysis. When 

 this condition is fulfilled it can be shown that the curve is always a 

 rectangular hyperbola, but a different one for each temperature at 

 which the observations are made. For haemoglobin solutions not freed 

 from salts or for blood or dilutions Of blood the curve is of a different 

 order altogether, a curve with a double contour (S-shaped). (Figs. 120, 

 121). If to a solution of haemoglobin freed from salts and yielding a 

 rectangular hyperbola as its dissociation curve, salts be added in the 

 quantities and of the kind known to exist in dog's blood, the curve of 

 no 



7 



is &a 

 16 ec 

 14 cc 

 1 2 co 



IOC& 



see. 



6 C.C 

 4CC. 



2 C.C. 



03C.C, 



10 to 30 40 10 M 70 80 00 100 110 120 130 140 ISO 



Fig. 120. Curves of Dissociation of Oxygen for Horse's Blood (B) and Dog's Hemo- 

 globin solution (H) at 38 C. (Bohr). The figures along the base-line are the 

 partial pressures of oxygen to which the bLood and haemoglobin solution were 

 exposed. Those along the vertical axis on the left are the percentage saturations 

 with oxygen. The figures along the vertical at the right give the actual number 

 of c.c. of oxygen chemically combined by 100 c.c. of the blood for each pressure 

 of oxygen. The interrupted line P indicates the amount of oxygen dissolved in 

 the plasma of the blood at each partial pressure on the assumption that the 

 plasma is two-thirds of the volume of the blood. Thus, at 150 mm. oxygen 

 pressure the plasma of 100 c.c. of blood took up 0-3 c.c. oxygen. 



dissociation given by dog's blood is obtained. The addition of the 

 salts appropriate to human blood in the proper amounts causes the 

 hyperbolic curve of the pure haemoglobin solution to change into an 

 S-shaped curve, such as is given by human blood, and so on. 



The foundation has thus been removed from the theory that 

 different animals possess haemoglobins differing in their capacity 

 to take up oxygen. The salts are supposed to alter the dissociation 

 curve, by changing the degree of aggregation of the haemoglobin 

 molecules- i.e., by causing them to adhere to each other to a greater 

 or less extent according to the quantity and kind of salts present. 



Another factor which greatly influences the binding power of 

 haemoglobin for oxygen, and therefore the dissociation curve, is 

 the reaction of the blood (p. 24). When the hydrogen-ion concen- 



