X PREFACE TO SECOND EDITION 



connection with the physical and chemical examina- 

 tion of milk. 



The author hopes that, by the radical changes indi- 

 cated, the usefulness of the book may be extended, and 

 that the study of applied bacteriology may be en- 

 couraged. I am under special obligations to Professor 

 Edwin O. Jordan for advice and suggestions as to the 

 general plan of the book, to Dr. Mary Hefferan for 

 critical reading of the manuscript and the proof, and 

 to Dr. R. E. Buchanan for valuable advice in outlining 

 the course in soil bacteriology. 



Paul G. Heinemann 

 June, igii 



PREFACE TO THIRD EDITION 



In this third edition the general plan of the book 

 has not been changed. The progress of science 

 necessitated alterations and additions which have 

 been incorporated in the text. A fermentation chart 

 of cardboard has been added to the colony counter 

 in the back cover. 



The author is under obligations to Professors 

 Edwin O. Jordan and Norman MacLeod Harris for 

 valuable suggestions. 



Paul G. Heinemann 



June, 1915 



