S52 ANNUAL REPORT OF THE Off. Doc. 



JJaiijiug has uudeigoue luauy prolouud changes duiiug the last 

 geueration, aud more paiticularlj during the last iifteeii years. 

 This is true of both the agricultural aud the manufacturing phases 

 of dairying, ^\'e can fully realize this by «)o(iciug the changes iu 

 its very language. Even teu years ago few dairymen would have 

 been able to use intelligently, if at all, many of the expressions that 

 are very common now, such as bacteria, lactic acid fermentation, 

 pasteurization, sterilization, separator cream, ripened cream, fat 

 basis for paying dividends, ripeniog tests, etc., etc. With all the 

 advance in knowledge and the improvement in practice that we have 

 witnessed iu recent times, there are still many unsolved problems in 

 dairying; but we do well to be impressed with the great things which 

 have already been accomplished and to appreciate the advantageous 

 position we are now in for making further progress, compared with 

 the position we were in only fifteen years ago. 



These changes for the better have been brought about through the 

 combination of a variety of educational agencies, among v^hich may 

 be mentioned our agricultural experiment stations, dairy schools. 

 State Departments of Agriculture, farmers' institutes, the agricul- 

 tural press, farmers' clubs, etc. 



Our dairy products, as a result of improved methods of producing 

 milk and of improvement i« manufacturing processes, are greatly 

 superior on the average to those we made half a generation ago. 

 The consuming public has, to some extent, become more choice in 

 its tastes and exacting in its demands; in other words, the present 

 standards required for dairy products are higher than they were. 



The object of this little treatise is to present, with a moderate 

 degree of fullness, some of the results of these recent years of pro- 

 gress, so as to give the reader some idea of what conistitutes '^Modern 

 Dairv Science and Practice." 



CHAPTER I. 



THE CHEMISTRY OF MILK. 



1. General Composition of Milk. 



In milk, as well as iu most of its commercial products, we find 

 the following compounds and classes of compounds: 



(1) Water. 



(2) Fat. 



(3) Nitrogen compounds or proteids. 



(4) Sugar. 



(5) Salts or asb. 



(6) Gafiea. 



