The ferment acts best when the milk is lukewarm, but it will do the work at temperatures ranging from 50°, or even lower, to 120° F. Strongly pasteurized or sterilized milk will not curdle with rennet, but milk pasteurized at a low temperature is not changed enough to prevent it from making a firm curd. More rennet does not make a firmer curd but causes the milk to curdle quicker; less rennet makes the process slower. Diluted milk will not curdle firmly, and the failure of milk to make a smooth coagulum of the usual consistency and in the usual time, the temperature being right and the regular amount of a standard rennet being used, is a never-failing proof that something is the matter with the milk. It has been changed from its natural condition by over-heating in pasteurization or by watering or doctoring, or it has not been properly ripened. Footnote 9: W. O. Atwater, Farmers’ Bulletin No. 142. Footnote 10: Dr. E. V. McCollum in “Hoard’s Dairyman.” Footnote 11: Prepared for “The Story of Milk” by A. Louise Andrea. ------------------------------------------------------------------------ BIBLIOGRAPHY Cheese Making; John W. Decker, Columbus, O. The Milk Question; M. J. Rosenau, Houghton-Mifflin Co., Boston. The Manufacture of Cheese of the Cheddar Type from Pasteurized Milk; J. L. Sammis and A. T. Bruhn, Bulletin 165, Bureau of Animal Industry, Washington, D. C. Dairy Laboratory Guide; Charles W. Melick, D. Van Nostrand Company, New York City. Handbook for Farmers and Dairymen; F. W. Woll, John Wiley & Sons, New York City. Testing Milk and Its Products; E. H. Farrington and F. W. Woll, Mendota Book Company, Madison, Wis. Farmers’ Clean Milk Book; Dr. Charles E. North, John Wiley & Sons, New York. Ost og Osteproduktion; G. Ellbrecht, Nordisk Forlag, Copenhagen, Denmark. Outlines of Dairy Bacteriology; N. L. Russell, Madison, Wis. A B C in Butter Making; J. H. Monrad, Urner-Barry Co., New York. A B C in Cheese Making; J. H. Monrad, Urner-Barry Co., New York. Dairy Chemistry; Henry Droop Richmond, Charles Griffin and Company, Ltd., London. Milk, its Nature and Composition; C. M. Aikman, Adams and Charles Black, London. Milk and Its Products; H. H. Wing, The Macmillan Co., New York. Principles and Practice of Buttermaking; G. L. McKay and C. Larsen, John Wiley & Sons, New York. Science and Practice of Cheese Making; L. L. Van Slyke and Chas. A. Publow, Orange Judd Company, New York. Agricultural Bacteriology; H. W. Conn, P. Blakiston’s Son & Co., Philadelphia. Creaming Milk by Centrifugal Force; J. D. Frederiksen, Little Falls, N.Y. The Common Sense of the Milk Question; John Spargo, The Macmillan Company, New York. Practical Dairy Husbandry; X. A. Willard, Excelsior Publishing House, New York. Maelkeri Bakteriologi; Orla Jensen, Copenhagen.