leading periodicals dealing with the subject. Thus the latest information has been incorporated.

No attempt has been made to give detailed references in a work of this character.

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 Projection 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, Ill.; Bausch & Lomb Optical Company, Rochester, N. Y.; Creamery Package Manufacturing Company, Chicago, Ill.; Davis Milk Machinery Company, North Chicago, Ill.; Mr. C. B. Hoover, Superintendent of Sewage Disposal Plant, Columbus, O.; Mr. C. P. Hoover, Superintendent of Water Filtration Plant, Columbus, O.; The Hydraulic Press Manufacturing Company, Mt. Gilead, O.; Loew Manufacturing Company, Cleveland, O.; Metric Metal Works, Erie, Pa.; Sprague Canning Machine Company, Chicago, Ill.; 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.