PREFACE TO FIFTH EDITION 



The book has been thoroughly revised and in part rewritten. Five 

 additional chapters have been inserted, in order to increase the useful- 

 ness of the volume and to keep thoroughly abreast with recent develop- 

 ments in Physiological Chemistry. The new Chapters are, Chapter VI 

 on Nucleic Acids'and Nucleoproteins, Chapter VIII on Gastric Analysis, 

 Chapter XI on Intestinal Digestion, Chapter XVI on Blood Analysis 

 and Chapter XXVII on Metabolism. 



The Chapter on Metabolism consists in large part of directions 

 for typical metabolism tests which may be conducted by the student in 

 order to demonstrate important principles of metabolism. 



The Chapter on Blood Analysis includes the most recent methods 

 which have played such an important part in 'adding to our knowledge 

 regarding the composition of the blood under normal and pathological 

 conditions. 



The Chapter on Gastric Analysis includes a general discussion of 

 titratable acidity and hydrogen-ion concentration as well as an expo- 

 sition of the Fractional Method of Gastric Analysis which was elabo- 

 rated in the author's laboratory by Dr. Martin E. Rehfuss, and which 

 has been very widely adopted. 



The Chapter on Nucleic Acids and Nucleoproteins is a brief dis- 

 cussion of basic facts accompanied by experiments suitable for student 

 use. 



In order to facilitate the selection of tests and methods for courses 

 in which but little time is devoted to the subject, the actual laboratory 

 procedure involved in such tests and methods as the author considers 

 most important has been printed in black face type to differentiate 

 such tests and methods from those which he considers of less impor- 

 tance, which are set in small type. In certain instances, however, tests 

 and methods which the author believes to be of first importance, but 

 which are not so readily adapted to student use, have been printed in 

 small type. 



The latest and best methods of quantitative analysis have been 

 introduced throughout the volume. The nephelometer has been dis- 

 cussed and certain nephelometric methods described. 



Certain tests and methods which had obviously outlived their 

 usefulness have been omitted from this edition. Others which the 



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