VI PREFACE. 



incorporated in the text, the folding tables, which have 

 proved cumbersome in use, having been eliminated. 



The Publishers have spared no expense to meet my 

 views on the re-arrangement, and the book has been 

 carefully set up and revised without being rushed; the 

 latest researches have been incorporated, those appearing 

 while the work was in the press being included as 

 addenda, and it is hoped that the additional matter, as 

 well as the re-arrangement, will render the book of 

 increased service. 



Thanks are due to the Editor of the Analyst, to 

 the National Clean Milk Society, and to various firms 

 for the supply of blocks. 



H. D. R. 



July, 1920. 



