512 EXPERIMENT STATION EECORD. 



years, on the basis of which tables have been prepared Avhich give us 

 a very good general idea of the average composition and digestibility 

 of feeding stuffs and of the extent of their variations. Somewhat 

 later, so-called " feeding standards " were propounded in which it 

 was attempted to formulate the amounts of the several nutrients best 

 adapted to the various purj^oses of production. The general accept- 

 ance of this point of view was largely brought about by the writings 

 of Wolff. The whole made a complete and simple system. So much 

 is required for a certain purpose. This feed will furnish so much 

 and the other so much. It is simply a question of arithmetic to work 

 out a suitable combination, and a machine has even been devised for 

 this purpose. 



This system was introduced to the American public after it had 

 assumed quite a definite form and it may be said in all fairness to still 

 be, to a considerable extent, the basis of our theory. We question 

 some of the standards, some of them we have modified, we hold them 

 more flexibly than Ave once did. but protein, carbohydrates and fat 

 are still the feeding trinity. Our theory of nutrition has become tra- 

 ditional, and has little pedagogic value for the student and little 

 inspiration for the investigator. As a natural result it is more or 

 less out of touch with practice, while our experiments, upon the 

 theoretical side of the subject, have been " marking time.'' 



With the publication of the results obtained by Zuntz and his asso- 

 ciates upon the work of digestion, and of Kiihn's and Kellner's 

 respiration experiments at Moeckern, a new stage of progress was 

 entered upon, to which I venture to hope that our own station in 

 Pennsylvania has contributed a little. While the results of these 

 investigations are best and most conveniently expressed in terms of 

 energy, that is not the essential point. The vital thing is that in these 

 experiments the amount of production due to each material experi- 

 mented upon has been actually determined, with at least a fair degree 

 of accuracy', by the laborious methods of the respiration apparatus 

 or the respiration calorimeter. Enough results have already accu- 

 mulated to show that many of the old values assigned to feeding 

 stuffs vary widely from the truth. In particular these investigations 

 have demonstrated the inaccuracy of the fundamental assumption 

 upon which we have been liasing our comparisons of feeding stuffs, 

 viz, that digestible matter from different sources is equally valuable. 

 For example, an experiment at the Pennsylvania Station showed the 

 digestible organic matter of corn meal to be twenty-one per cent 

 more efficient for maintaining a steer than the same amount of digest- 

 ible matter from timothy hay, and fifty-six per cent more effi- 

 cient for fattening. Kellner estimates the value of the digestible 

 matter in numerous coarse feeds at only twenty to thirty per cent of 



