Studies in Milk Secretion. 97 



average variation for two and three-year olds is practically the 

 same, and about three-tenths of one per cent lower than 

 among the older cows. 



If the variation in per cent of fat be averaged according to the 

 groups given in Table IV, a striking similar it}- is found between 

 the averages for the different groups as can be seen from the 

 figures here given. 



No. of 



Group. Average Variation. 



I. Cows tested i to 15 days from calving 1.62 



II. " " i6t030 '' " " 1.60 



III. " " 31 to 60 " " " 1.59 



IV. " " more than 60 days from calving 1.60 



Average of all 1.60 



In the table below are given two instances under each age of 

 individual variation in per cent of fat. — one for the greatest 

 and one for the least variation. Along side of the greatest 

 variation for the week is given the greatest variation for one day 

 and also the pounds of milk and per cent of fat for each milking on 

 that day, together with the total fat for the day. There is also 

 given the sani*^ data for the day on which the least variation 

 in the per cent of fat occurred, and finally the total fat for the 

 week. Moreover, in order to compare these animals showing so 

 great and so little variation with animals of the same class, there 

 is also given under each age the largest, smallest and average 

 weekly 3deld of fat for that age. 



