New York Agricultural Experiment Station. 81 



ment of this Station, who suggested the original plan of this work 

 and aided in carrying it out; also to the Geneva Milk Company 

 and the White Springs Dairy Company for courtesies shown. 

 Acknowledgment of help received is likewise due Dr. Robert S. 

 Breed under whose direction the work has been published. 



HISTORICAL. 



In the early history of the microscope, scientists conceived the 

 idea of utilizing it as a means of counting the number of bacteria 

 present in various substances. In fact, Leeuwenhoek, in 1683 in 

 his earliest description of bacteria, gives an estimate of the number 

 he saw in tartar from teeth based on what his primitive microscope 

 revealed. A development of this technique came during the years 

 from 1877 to 1890 during which time such men as Naegeli, Lister, 

 Fritz, Pasteur and others used the microscope as a means of esti- 

 mating the number of bacteria or yeasts present in given substances 

 as a preliminary step in the making of pure cultures. When solid 

 culture media were introduced and petri plates came into general 

 use, the microscopic method of counting bacteria passed into the 

 background and since that time the greater number of bacterial 

 counts have been made by the plate method. So far as can be 

 ascertained, Eberle 1 was the first to make careful determinations 

 of the number of bacteria present in dried, stained films by the 

 use of the microscope. In this case the films were prepared from 

 feces. Similar quantitative studies of fecal bacteria were made 

 later by Winterberg, 2 Klein 3 and Hehewerth. 4 MacNeal, Latzer 

 and Kerr 5 have published the results of investigations in which 

 the combined Eberle-Klein methods and the Winterberg method 

 were used. Winslow 6 devised a microscopic method for quantitative 



1 Eberle, Robert. Zahlung der Bakterien im normalen Sauglingskot. Centbl. Bakt. 



Abt. I, 19:2-5. 1896. 



2 Winterberg, Heinrich. Zur Methodik der Bakterienzahlung. Ztschr. Hyg., 



29:75-93. 1898. 



3 Klein, Alex. Eine neue mikroskopisehe Zahlungsmethode der Bakterien. Centbl. 



Bakt., Abt. I, 27:834-835. 1900: Die physiologische Bakteriologie des Darm- 

 kanals. Arch. Hyg., 45: 117-175. 1902: Bemerkung zu der Arbeit Dr. Max 

 Lissauers "Ueber den Bakteriengehalt menschlicher und tierischer Faces." Arch. 

 Hyg., 59 : 283-285. 1906. 



4 Hehewerth, F. H. Die mikroskopisehe Zahlungsmethode der Bacterien von Alex. 



Klein und einige Anwendungen derselben. Arch. Hyg., 39 : 321-389. 1900. 



6 MacNeal, Ward J., Latzer, Lenore L., and Kerr, Josephine E. The fecal bacteria 

 of healthy men. Journ. Infect. Dis., 6 : 123-169, 571-609. 1909. 



6 Winslow, C-E. A. The number of bacteria in sewage and sewage effluents deter- 

 mined by plating upon different media and by a new method of direct micro- 

 scopical enumeration. Journ. Infect. Dis., Suppl. No. 1 : 209-228. 1905. 



6 



