Relation of Fat to Casein. 159 
Van Slyke,* in a series of investigations extend- 
ing over several years, and including the milk of not 
less than fifteen hundred different cows, found that as 
the percentage of fat increased the percentage of 
casein increased in a nearly constant ratio; or, to 
quote his own words: “While we have noticed con- 
siderable variation when we considered individual 
herds, we have found that, as a rule, there were two- 
thirds of one pound of casein for each pound of 
fat in the milk, whether the milk contained 3 or 4 
per cent of fat; though this normal relation was con- 
siderably affected in the season of 1893 by the effects 
of drought upon the pastures. * * * * When 
the amount of fat in the milk increased beyond 474 
per cent, there was a gradual but slight diminution 
of casein for each pound of fat.” 
The accompanying tables give the data upon which 
Dr. Van Slyke’s opinions were based : 
Table showing relation of fat to casein in normal milk. 
| Average 
, Ape ; Tainber of Average per Average per pounds of 
NOU: aati, | “aczmples, [ME OE Aan enna iaein| aan Soe 
fat. 
I. 3 to 3.5 22 3.35 2.20 0.66 
I. 3.5 to 4 112 3.72 2.46 0.66 
Il. 4 to 4.5 78 4.15 2.70 0.65 
IV. 4.5 to 5 16 4.74 3.05 0.64 
Vv. 5 to 5.25 it 5.13 3.12 0.61 
*New York Agricultural Experiment Station, Bulletin, No. 68, New Series. 
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