PREFACE. 
THE revolution in dairy practice brought about 
by the introduction of the centrifugal cream  sepa- 
rator and the Babcock test for fat and by a more 
definite knowledge regarding the various fermenta- 
tions that so greatly influence milk and the manu- 
facture of its products, has seemed to demand the 
. publication of a small handbook that shall give 
to the dairyman, and particularly to the dairy 
student, in simple, concise form, the principles un- 
derlying modern dairy practice. In attempting to 
meet this demand, I have had largely in view the 
needs of my own students, while still keeping in 
mind the general dairy reader. 
In the collation of the information, where so 
many points are still unsettled, it is of course dif- 
fieult in all cases to distinguish fact from conjec- 
ture. The aim has been at all times to give 
the present state of knowledge as supported hy 
the weight of evidence and the opinions of those 
whose authority is highest. In how far this has 
been successful time alone can tell. It would be 
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