


LW ere ug Fa \ 
ia rye, é £ 
NITROGENOUS FEEDING STUFFS. IOQ 
of butter-fat. In general the results accord with those obtained 
from the other American experiments above summarized. 
It would be very interesting to summarize the results of 
European experimenting upon this subject, putting them in 
such form as to show in full detail their bearing upon the 
special questions here under consideration. Such a treatise, 
however, would exceed the bounds of the present report, and, 
furthermore, the European work has been discussed so fre- 
quently and in so much detail in other publications that the 
treatment here is hardly necessary. 
UNDETERMINED FACTORS IN EXPERIMENTS OF THIS KIND. 
In connection with experiments of this class, as they have 
been carried out both in this country and Europe, there is one 
question which has perhaps received too little consideration. 
It is this: In how far do experiments of short duration, con- 
tinuing, as these have generally done, only from one to four 
weeks, or thereabouts, indicate what would be the effects of 
similar feeding if it were continued for a longer time, as, for 
instance, during the whole period of lactation? And further: 
What would be the effects of the same feeding if practiced con- 
tinuously year after year? In other words, Is any special 
physiological influence exerted by a given ration, fed for a 
short time, which would not be maintained if the feeding were 
continued? Or, on the hand, Is there any possible effect of a 
given ration, which does not appear in a short test, but which 
might be gradually developed? 
Of course to ask such questions as these is to imply a meas- 
ure of doubt regarding the reliability of nearly all the experi- 
mental inquiries that have been carried out in this and similar 
lines. For this doubt there may be no valid reason, but it 
cannot be said that no such doubts exist. 
These questions, furthermore, are such that a positive answer 
cannot be obtained without a large amount of laborious and 
time-consuming inquiry. Nevertheless, the subject is worthy 
-of the thoughtful consideration of investigators. 
Regarding the food also there are details which need to be 
examined more closely. One of these is the total quantity of 
the food. ‘This is, perhaps, best measured by the potential 
energy or fuel value of the digestible nutrients. In the 
