60 DATA FOR MILK INSPECTION. 



variation in the proportion of ingredients occurs during 

 the year. The poorest quality occurs during the first 

 half of the year, especially in April. A low figure is 

 also frequently noted about July. In the fall the 

 quality rises, being highest in October and November. 



The diagram shows that the variations in the total 

 solids are due mainly to the variations in fat, but not 

 entirely, for an increase in the proportion of fat is 

 usually attended by a slight increase in the non-fatty 

 solids. 



The earlier tendency was to assign too high a limit 

 for the non-fatty solids, since this figure was obtained 

 by methods which failed to extract all the fat. In 

 applying, therefore, the more modern processes, nor- 

 mal milk will be found to yield a figure for the non- 

 fatty solids decidedly below the extreme limit of 9.5 per 

 cent. Even 9 per cent, for the non-fatty solids is more 

 than is usually present. 



While it may be permissible in special cases, such 

 as the purchase of milk under contract, or in the oper- 

 ation of a large dairy, to reject samples which yield 

 below nine per cent, of non-fatty solids, it is not 

 just to exact such a standard for purposes of pub- 

 lic inspection, and as a basis for penal proceedings. 

 The standard of the Society of Public Analysts of 

 England (8.5 per cent, of non-fatty solids), has been 

 found satisfactory in the large experience of the mem- 

 bers of that body, and recently Dr. Vieth has ex- 

 pressed himself as follows : 



