NON-FATTY SOLIDS 45 



and increase during the autumn and winter seasons. The sep- 

 aration of the constituents forming the non-fatty portion of 

 solids makes it apparent that the decrease in the summer 

 months is due chiefly to the smaller proteid content, the lac- 

 tose and ash remaining fairly constant. The author's results 

 for Ottawa milks also show a tendency towards a decline in the 

 non-fatty solids during the summer months, though the varia- 

 tions are more irregular than in the series of Richmond given 

 above. In these results the proteid was also the greatest variant 

 and usually accompanied the variations in the fat content. 



Richmond ^^ found no difference between the non-fatty 

 solids of evening and morning milk on calculating the average 

 results for a number of years. Eckles and Shaw ^ also found 

 no appreciable difference in the total amount of non-fatty solids 

 in morning and evening milk, but their results show that this 

 is due to an increase of proteid in the morning milk with an 

 equivalent reduction in the lactose content. 



The effect of the stage of lactation upon the solids-not-fat 

 has also been reported upon by Eckles and Shaw.^ The lac- 

 tose remained comparatively constant (vide Table XIX) during 

 the greater portion of the period with a slight decline during 

 the last two to three months. The ash was constant and the 

 proteid decreased and increased sympathetically with the fat 

 though not in direct proportion to it. 



This sympathetic relation between the amount of fat and 

 proteid in milk has led to the introduction of several formulae 

 for the calculation of the proteid content from that of the fat. 

 Timpe suggested the formula P = 2+0.35F in which P and F 

 represent the percentages of proteid and fat, and gave many 

 analyses in support of it, but Richmond has pointed out that 

 when the series is extended, the agreement practically disap- 

 pears. Van Slyke's formula ^^ P = 0.4(F-3.0)+2.8, is to be 

 preferred to that of Timpe but cannot be considered as entirely 

 satisfactory. These formulae are calculated from the averages 

 of many analyses^ and represent the average relation between 

 fat and proteid in normal milk. Whilst this is of considerable 



