LIMITS AND VARIATIONS 



41 



during the winter. The fat content of the milk of Massa- 

 chusetts and Ontario shows several modes during the year, 

 although the average values for the summer months are less 

 than those for the winter months. Diagram No. I shows the 

 monthly variations in England for 1897-1913, as compiled 

 by Richmond, in Massachusetts as reported by Lythgoe of 

 State Board of Health, and in Ontario as calculated from the 

 Ottawa analyses of the author. Lythgoe has suggested that 



Diagram No. I 



EFFECT OF SEASON ON FAT CONTENT 



4.1 



4.0 



:3.9 



§3.8 



I 



3.7 



3.5 



Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 



the irregularities in the curve for the Massachusetts supply, as 

 compared with Richmond's results, are due to the larger number 

 of samples examined by the latter. Lythgoe's results, however, 

 are calculated from approximately 13,000 samples examined 

 during three years, and the similarity of the curve to that 

 plotted from the author's analyses of over 9000 samples sug- 

 gests that the number of modes in the curves is not fortuitous, 

 but is due to seasonal variations together with variations caused 

 by changes of food peculiar to local climatic conditions. 



Richmond also found that there were slight daily variations 



