No. 6. DEPARTMENT OF AGRICULTURE. 679 



apparent digestibility was due to an extensive fermentation which 

 it underwent in the digestive apparatus, and on the basis of these re- 

 sults serious doubts were again raised as to its nutritive value. 

 More recently still, since the question of the expenditure of work 

 in digestion has been brought prominently forward, one noted inves- 

 tigator claims to have shown that in the horse all the energy of the 

 digested crude libre is consumed in its own digestion; that is, the 

 fuel is so poor that it takes all the steam it can make to run the 

 mechanical stoker. On the other hand, another equally distin- 

 guished investigator seems to have shown that some forms of crude 

 fibre when fed to ruminants are about as valuable sources of energy 

 as pure starch. 



I mention these fluctuations and divergences of opinion simply as 

 a striking illustration of the paucity of our present knowledge io 

 this field. If it be true, as it unquestionably is,that food is to be re- 

 garded primarily as a source of energy to the animal organism, it 

 is certain that before we can put the practice of stock feeding upon 

 a sound scientific basis we must know much more than we do now 

 about the amount of energy contaioed in diilerent feeding stuffs, 

 about the relative availability of this energy and as to how its availa- 

 bility is or may be increased or diminished by the conditions of the 

 feeding. It is the hope of the Pennsylvania Station to be able to 

 contribute something towards the enlargement of our knowledge in 

 these particulars. As I urged at the outset, while the work is prim- 

 arily scientific m its character, it is yet, as we believe, also practi- 

 cal because it is directed toward the laying of secure scientific 

 foundations upon which a rational practice may be built. 



