116 



HEMOGLOBIN 



and Heidelberger(20), assume that the isoelectric point of horse 

 haemoglobin is pH 6-78, at lower pH the haemoglobin acts as a base 

 and at higher pH it acts as an acid.- Further, it is assumed that the 

 molecule of haemoglobin contains four equivalents of iron. 



The table gives the number of equivalents of acid (italics) or alkali 

 (block type) which one molecule (mol. wt. about 70,000) unites with 

 at the pH stated. 



It may here be specially noted that the figures given are for horse 

 haemoglobin only, and would be somewhat different for the haemo- 

 globins of other animals — another instance of the specificity of 

 haemoglobin. 



I spoke of Fig. 37 as a crude presentation of the facts. Its crudity 

 may suitably be compared with the very beautiful quantitative state- 

 ment from the Rockefeller Institute of the relative quantities of 



