204 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [VI, II
Also, it is only fair to call attention to Mitchell's misstatement to the effect that
my law of maximum, normal nutritive value " advocates the use of completely
balanced rations in the determination of net energy values ". In publishing this
principle I did not mention " completely balanced rations ", but did use the
expression " a ration which is qualitatively complete and quantitatively sufficient "
—which has a distinctly different meaning in that the idea of a complete diet
provides only for the presence of all required nutrients, in the necessary quantities,
while the perfectly balanced ration literally— must not only be complete, but
must not contain an excess of any nutrient. It is true, however, that, at an
earlier date, I had—less carefully—used the expression " completely balanced
rations " in a similar discussion 3 . Proceeding further, Mitchell calls attention to
my statement that " an individual foodstuff expresses its normal and most char-
acteristic nutritive value—only as it is a part of a ration which is qualitatively
complete and quantitatively sufficient . . . . ". The question which Mitchell raises
is, in reality, " which is the normal and most characteristic value of a foodstuff—
that determined by its full potentialities, when it is adequately supplemented, or
by its limitations, when fed alone ? ". The difference is simply one of point of
view. It is normal to use feeding stuffs as components of approximately complete
rations ; they are not commonly fed alone ; and I have used the word " character-
istic " to mean " representative ".
Mitchell states that " the recent developments in the net energy conception,
initiated and defended by the Pennsylvania group, have tended to complicate the
problem of net energy determinations and perhaps even to discourage those who
have hoped to put the conception to practical use in the rationing of farm animals ".
There have been no recent developments in the net energy conception, so far
as I know. It remains as at first proposed, and it is as unassailable as the law of
conservation of energy. But there has been much new light cast upon the subject of
energy metabolism, and a. searching analysis of the problem of determining energy
values, in studies published from this institute—which however, should be dis-
couraging only to those who adhere to the objective of determining net energy
values of individual feeding stuffs as constants.
The idea of determining net energy values of rations, however, is worthy of
consideration. This is a logical deduction from the work of this institute. I have
made this deduction ; have advocated the determination of such values, and have
enumerated some of their apparent uses in the study of problems in the field of
animal production 3 .
In regard to Mitchell's speculations as to the cause of specific dynamic action,
the relation of the dynamic effects of nutrients to the combinations in which they
are fed, etc., we do not care to comment, especially since the methods of determi-
nation of specific dynamic effects, and the measurements of these effects—in the
3
Proc . Amer. Soc. Animal Production, Ann. Meeting, 1932 : 32—40.