W. Taylor and A. D. Hitsband 121 



DISCUSSION OF RESITLTS. 



It seems justifiable to conclude from the results of these experiments, 

 that with the exception of the non-protein nitrogen, which is not a 

 product of the mammary gland, diet has no direct influence on the 

 percentage composition of the milk. It has. however, an indirect influence 

 by reason of its effect on the daily volume, but the percentages in which 

 the various constituents of the milk will be present in any particular 

 daily volume, obtained by some special method of feeding, will be the 

 same as those in which they would be present in the same daily volume 

 were it obtained in the ordinary course of lactation. 



Indeed, the inverse relationship of percentage of fat and daily volume 

 is so unvarying on the average, as Tocher (7) points out in the case of the 

 cow — in his statistical analysis of milk records, where he deals with the 

 milk of thousands of cows — that it may be stated, and illustrated by a 

 graph, with the mathematical precision of a proposition in Euclid. He 

 says: "It will be seen that there is a direct proportional relationship 

 between quantity and average quality. 



"Given two known values of average quahty for any two types of 

 quantity, a straight line joining the two values of average quality and 

 extended on either side will give the average quahties for all other types 

 of quantity, average quahty being represented in value by a straight 

 line proportional to its value standing at right angles to the base line 

 of quantity at a point corresponding to its appropriate type of quantity." 



By the term " quality "' in the above statement is understood, of 

 course, the percentage of fat. 



While this is true of the fat it is probably no less true of the protein. 

 Throughout the present investigation the percentage of protein in the 

 milk and the daily volume varied inversely with a regularity at least equal 

 to that of the fat. It is true that these percentage variations were not 

 so marked as in the case of the fat, the inverse rise and fall with each 

 variation in volume having been less, as a rule, but they took place from 

 da)^ to day with an equal consistency if to a less degree, even during 

 periods of special dieting. 



The probabihty is, therefore, that it will be found from a statistical 

 analysis of milk records — when the requisite data become available — 

 that the relationship of average percentage of protein to each particular 

 daily volume can be formulated as clearly and precisely in the case of 

 this constituent of the milk as has been done by Tocher in the case of 

 the fat. It is true that in a graph the hne representing the fat and that 



9—2 



