New Yokk Agricultural Experiment Station. 115 



water content, but an actual increase of fat secretion by the mammary 

 glands, as is mo.st strikingly shown by the middle line in period 4 

 of Fig. 3, recording an actual fat increase at the time of a milk 

 decrease. The relative differences in the fat production in the 

 several experiments, induced by the change in the rations were 

 not constant. In experiment I this difference amounted to 

 24 per ct. of the total fat, while in experiments II and III, it was 

 only 5 per cent; in experiment IV the differences in the fat output 

 of the several periods were relatively greater than in the previous 

 work, but the largest difference was less than the largest difference 

 in experiment I. 



The period of phosphorus equilibrium shows the most favorable 

 fat and milk production, which in this particular instance amounts 

 to seven ounces fat and tAvo and one-half pounds of milk per week 

 in excess of the production on the normal rations. This can readily 

 be explained by the assumption that the change in the ration was 

 sufficient to change the milk flow but not enough to lower the rela- 

 tive amount of fat in the milk. If further experiments estabhsh 

 this as a physiological fact it will be interesting scientifically and 

 practically suggestive. 



Aside from the fat, the tables show but a relatively small change 

 in the composition of the milk. Since the fat has been shown to 

 vary with the rations, it should be deducted from the total solids, 

 before a study of the solids is undertaken. In Table VII, in which 

 the average composition of the milk for each period is given, the 

 fat-free solids and the fat-free, ash-free solids are listed in columns 

 six and eight. The differences between the percentages are small 

 for both the solids and the ash. The small variations seem to follow 

 the changes in the milk flow, so that the actual increase in the milk 

 solids resulting from the decrease in the phosphorus in the ration 

 is somewhat more pronounced than the changes in the milk volume, 

 the same being true of the decrease when calcium phytate was added. 

 The increased milk flow may therefore be considered as a true 

 secretion of milk and not a mere dilution analogous to polyuria. 



Table VII. — Yield and Composition of the Milk in the Several Periods. 



