50 



THE NORMAL COMPOSITION OF MILK 



ment of proteid is more than counterbalanced by the constancy 

 in the lactose and mineral matter. 



The percentage of ash in milk is comparatively constant but 

 small variations are observable and depend upon variations in 

 the proteid content, as a portion of the ash is combined with the 

 caseinogen to form the caseinogen complex. Richmond has 

 deduced the formula 4 =0.36 +0.1 IP, in which A and P rep- 

 resent the percentages of ash and proteid, for the calculation of 

 the ash content. 



It is upon the above basic relations between the amounts of 



the various constituents in milk that the formulae of Van Slyke, 



T S 

 previously referred to, and that of Olsen^^, P=T. S. — -^' 



are based. Lythgoe has suggested that lactose may be cal- 

 culated from the following formula. 



L=T. 



S.-[f+0.7+{t.S.-^)], 



from Olsen's formula and 



L=T. S.-[F+0.7+{0A(F-3)}+2.8], 

 from Van Slyke's formula. ' The ash in these formulae is 

 assumed to be 0.70 per cent, but it would be preferable to sub- 

 stitute Richmond's formula of A=0.36+0.11Pforthe assumed 

 value. 



All the foregoing refers only to whole milk, that is, the mixed 

 milk obtained by continuous milking until the udders are dry. 

 The variations due to partial milking are very striking and 



Table XXVI 



(Boussingault) 



