THE SPECIFICITY OF HEMOGLOBIN 



45 



dissociation curve of Arenicola was determined, and this appeared to be 

 different from that of human haemoglobin under similar circumstances, 

 i.e. in a dilute solution of known strength and buffered to a given 

 hydrogen-ion concentration (8). 



Since that time the oxygen dissociation curves of haemoglobins 

 from a number of different species have been investigated, many of 

 them by Ma9ela and Seliskar(ii). They are all different. The difference 

 cannot be stated by a simple constant because it depends upon the 

 temperature. Figs. 8 and 10 show, however, that frog's haemoglobin 

 holds to its oxygen with much less tenacity than that of some 

 of the low forms of life. 



12 3^5676 



— ♦ d wtn. He^ 



Fig. 9. Approximate Og dissociation curve of human haemoglobin in dilute solution 



at different temperatures. 



The remarkable effect of temperature on the dissociation curve of 

 human haemoglobin is shown in Fig. 9. The comparison may be 

 expressed thus : 



In round numbers therefore the pressure corresponding to 50 per 

 cent, saturation rises fivefold for every rise of temperature of 10° C. 



