VI PREFACE 



The photomicrographs are original except where otherwise 

 indicated and are all of a magnification of one thousand 

 diameters where no statement to the contrary appears. 

 These photographs were made with a Bausch & Lomb Pro- 

 jection Microscope fitted with a home-made camera box. 

 Direct current arc light was used and exposures were five 

 to ten seconds. Photographs of cultures are also original 

 with a few indicated exceptions. All temperatures are 

 indicated in degrees centigrade. 



For use of electrotypes or for prints furnished the author 

 is indebted to the following: A. P. Barber Creamery Supply 

 Company, Chicago, 111.; Bausch & Lomb Optical Company, 

 Rochester, N. Y.; Creamery Package Manufacturing Com- 

 pany, Chicago, 111.; Davis Milk Machinery Company, N. 

 Chicago, 111.; Mr. C. B. Hoover, Superintendent of Sewage 

 Disposal Plant, Columbus, 0.; Mr. C. P. Hoover, Super- 

 intendent of Water Filtration Plant, Columbus, 0.; The 

 Hydraulic Press Manufacturing Company, Mt. Gilead, O.; 

 Loew Manufacturing Company, Cleveland, O.; Metric 

 Metal Works, Erie, Pa. ; Sprague Canning Machine Company, 

 Chicago, 111.; U. S. Marine Hospital Service.; Wallace and 

 Tiernan Company, New York City, N. Y. 



For the preparation of many cultures and slides, for great 

 assistance in the reading of proof and in the preparation of 

 the index. Miss Vera M. McCoy, Instructor in Bacteriology, 

 deserves the author's thanks. 



The author trusts that the book will find a place in College 

 and University courses in Bacteriology. 



C. B. M. 



CoLtTMBtrs, 1917. 



