New York Agricultural Experiment Station. 65 



been publis^ied.^ In this bulletin, while the author accepts the 

 responsibility for all conclusions drawn from the data, he takes 

 pleasure in acknowledging the important activities of his col- 

 leagues in planning and executing the experiments. 



Recognition should be given to the work of Mr. L. A. Rogers 

 who, as Assistant Bacteriologist during a portion of the investiga- 

 tion, had charge of the routine bacteriological examinations. 

 Since his transfer to the Department of Agriculture at Washing- 

 ton his part of the investigation has been carried on by his suc- 

 cessor, Mr. J. F. Nicholson. 



ROLE OF LACTIC-ACID BACTERIA. 

 lactic-acid bacteria are constantly present in factory 



MILK, 



Everyone knows that fresh milk left in a warm room sours 

 rapidly and nearly everyone knows that this souring is due to the 

 formation of acid by bacteria. Since milk drawn with certain 

 precautions does not undergo this rapid souring it is plain that 

 these bacteria find their way into the milk after it is drawn. 



Because the acid formed during this souring process is prin- 

 cipally lactic these various acid-forming species were early spoken 

 of collectively as the lactic-acid bacteria. Without knowing ex- 

 actly why, it was found that the formation of acid by these germs 

 was a necessary part of the manufacture of cheddar cheese and in 

 order to insure the presence and activity of the most desirable 

 kinds it has long been the custom to begin the process of manu- 

 facture by adding considerable quantities of so-called " starter." 



IVan Slyke, L. L., Harding, H. A., & Hart, E. B. A Study of Enzymes in 

 Cheese, N. Y. Agr. Exp. Station Bui. 203. (1901.) 



Van Slyke, L. L., & Hart, E. B. A Study of Some of the Salts Formed by 

 Casein and Paracasein with Acids. N, Y. Agr, Exp. Station Bui. 214, 

 (1902,) 



Van Slyke, L. L., & Hart, E. B. Methods for the Estimation of Proteolytic 

 Compounds Contained in Cheese and Milk. N. Y. Agr. Exp. Station Bui. 

 215. (1902.) 



Van Slyke, L. L., & Hart, E. B. Some of the Compounds Present in Amer- 

 ican Cheddar Cheese. N. Y. Agr. Exp. Station Bui 219. (1902.) 



Van Slyke, L. L., & Hart, E. B. Relation of Carbon Dioxide to Proteolysis 

 in the Ripening of Cheddar Cheese. N. Y. Agr. Exp. Station Bui. 231. 

 (1903.) 



Van Slyke, L. L., Harding, H. A., & Hart, E. B. Rennet-Enzyme as a Fac- 

 tor in Cheese-Ripening, N. Y, Agr. Exp. Station Bui. 233. (1903.) 



Van Slyke, L. L., & Hart. E. B, Conditions Affecting Chemical Changes in 

 Cheese-Ripening. N. Y. Agr. Exp. Station Bui. 236. (1903.) 



