536 Bulletin 169. 



pounds, a decrease of nine per cent, would be represented by 91. 

 In like manner her daily average of 31 pounds during the third 

 period would be represented by 100. And so on through the 

 whole period of lactation we reckon the average daily yield of 

 each four weeks according to the ratio it bears to the yield in the 

 first four weeks w^hen considered as 100. The relative increase 

 or decrease in per cent of fat was determined in the same manner, 

 and is given in the table along with the variation in milk yield. 



Following this table are three plates showing lines pJatted 

 according to the figures given in the table. These lines show 

 very plainly the variation in milk and per cent of fat from month 

 to month. The record which each set of lines is intended to 

 display is indicated by the Roman numeral which corresponds 

 to the same number in table IV. Passing from left to right in 

 these plates, each perpendicular line represents four weeks ad- 

 vance in the lactation period, and each space between the hori- 

 zontal lines represents two pounds of milk or .2 of i per cent of 

 fat. Keeping these points in mind, the reader, beginning at 100, 

 will easily trace each record for milk and per cent, of fat as 

 given in table IV. 



