PREFACE TO SECOND EDITION 



THE present issue of the Laboratory Course in Serum Study 

 does not represent a new edition in that it has been found impos- 

 sible to completely revise the book at this time. There are, how- 

 ever, a number of important changes in protocols and technique 

 which have been made on the basis of experience hi giving the 

 course to medical and public health students. Most of these 

 changes are in the form of alterations hi the plan of experiments, 

 making them more easy to perform and more illustrative of under- 

 lying principles. In preparing these changes for the new printing, 

 we have been greatly aided by Dr. Samuel Cochran, Professor of 

 Bacteriology at the Shantung Christian University hi China, who 

 helped us hi giving this course at Columbia last year. 



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