Vlll PREFACE 



The scope of the book had of necessity to be strictly Umited. 

 Physicochemist, organic chemist, biochemist, physiologist, bacteriol- 

 ogist, botanist, zoologist, pathologist, and clinician are all interested 

 in various aspects of the subject. Our main emphasis is biochemical, 

 as the title is intended to indicate. Problems of organic structure 

 are dealt with only in so far as they are of importance for an under- 

 standing of the functional and metabolic aspects. More emphasis is 

 given to the physicochemical background. The chemistry of hemo- 

 globin and the hematin enzymes is so intimately linked with general 

 problems of protein chemistry that it is impossible to draw a clear 

 line of demarcation. Again, our selection has been guided by con- 

 sideration as to whether or not a connection could be established 

 between a particular property and aspects of function or metabolism. 

 On the other hand, the functional aspect of the hematin enzymes has 

 been considered from a chemical rather than from a biological angle; 

 the latter is to be found in works on biological oxidation and is beyond 

 the scope of this book. A large number of facts have been discussed 

 which may be of interest for clinicians and pathologists, but it should 

 be realized that they have been selected because they throw light on 

 aspects of normal metabolism, rather than from a general medical 

 viewpoint. 



It is obviously impossible to give a complete treatment of this 

 immense subject in a few hundred pages. Hemoglobin alone is 

 probably the most extensively studied biological product; many 

 thousands of research papers deal with it. No special apologies are 

 required for the omission of reference to many publications. The 

 purpose of this book, however, and the need for severe restriction of 

 the extensive bibliography necessitated other, more serious, omissions. 

 We have attempted to give due weight to pioneer work and have 

 treated in detail the latest publications in which our present knowl- 

 edge is most fully represented, but we have been forced to omit 

 reference to many papers in the intermediate period. At the time 

 of their appearance, these may have contributed greatly to our 

 knowledge. They are quoted, however, in the later publications 

 and may be readily found by a reference to the latter. 



We should explain why we elected not to cite in the text all author 

 names and to refer frequently to publications only by a reference 

 number. Again, this was necessitated by the dual purpose of the 

 book: to enable the student not specially interested in this particular 

 problem to read the text without interruption, and to permit the 



