PREFACE IX 



and endpoints, or to keep fermentation separate from 

 growth. All that is necessary is just a habit of thinking, 

 which is easily acquired. 



The literature available for the support of many 

 points discussed herein is inadequate. Allowing that a 

 considerable number of publications might have been 

 overlooked by me, the fact still remains that the avail- 

 able material is scanty. And yet, many experiments 

 have been made in the past which could have thrown 

 light on some debated points had they been recorded 

 fully instead of incompletely. Some essential facts, as, 

 the number of acting cells, the length of time of a fer- 

 mentation, or the quantity of inoculum in a growth 

 experiment have not been determined, or at least not 

 stated. Then, too often, data are given only in relative 

 numbers, without the key to absolute measure; while 

 results are given in curves only, from which it is impos- 

 sible to reconstruct the data with sufficient accuracy to 

 use them for any purpose. 



The making of a book usually involves not only the 

 author, but a number of his colleagues and associates. 

 This has been the case with this book, too. I am 

 obUged to Dr. J. M. Sherman, as head of the department, 

 for providing the opportunity for completing the manu- 

 script. I am obliged to him, as well as to Dr. F. W. 

 Tanner of Illinois University, for reading critically some 

 of the chapters. Several of my former and present associ- 

 ates, especially Mrs. Margaret N. Barnes, Miss A. Jean 

 Ferguson, M. J. Foter, P. Arne Hansen, and J. A. Woerz, 

 have been very helpful in correcting the style and read- 

 ing proof. Further, I have to thank Dr. H. H. Boysen, 

 Dr. D. C. Carpenter, Dr. Hermann Claassen, Mrs. V. A. 

 Coffeen and Dr. G. L. Peltier for permission to use some 

 of their unpublished data, and Drs. W. M. Clark, C. B. 



