iv PREFACE. 
longer be treated as one whole. For this reason such subjects 
as Testing Milk and its Products, Dairy Bacteriology, Cheese- 
making, and Technology of Milk and its Products, have not been 
treated comprehensively in this work. 
These lectures have been used, modified and changed, and 
under preparation for several years. At the present time the 
writers believe they are in such a condition as to warrant the 
publication of them. 
The authors admit that in our present state of knowledge it 
is in some instances difficult to distinguish well-established facts 
from those not so universally confirmed. It has been the object 
of the writers to give such information as is supported by the 
preponderance of experimental evidence. 
The authors are also indebted to the following parties for 
the use of electrotypes: Mower-Harwood Co., and Cherry Bros., 
Cedar Rapids, Ia.; Creamery Package Co., Waterloo Cream Sep. 
Co., and Iowa Separator Co., Waterloo, Ia.; Vermont Farm 
Machine Co., Bellows Falls, Vt.; Jensen Mfg. Co., Topeka, 
Kans.; Ox Fiber Brush Co., National Creamery Supply Co., 
International Harvester Co., Davis Cream Sep. Co., Borden & 
Selleck Co., and De Laval Sep. Co., Chicago, Ill.; Wagner Glass 
Works, and J. H. Monrad, New York, N. Y.; Burrell & Co., 
Little Falls, N. Y.; Empire Cream Sep. Co., Bloomfield, N. J.; 
Dairy Queen Mfg. Co., Flora, Ind.; Dairy Record, St. Paul, Minn., 
and W. D. Hoard, Ft. Atkinson, Wis. 
G. L. McKay, 
C. Larsen. 
Iowa State CoLtLece, Darry DEPARTMENT, 
