PROBLEMS IN ANIMAL NUTRITION. 511 



we have seemed largely content to borrow from foreign investigators. 

 To say this is not to deny the great value of much of the work done 

 b}' our stations, nor to decry the publication of useful information. 

 Nevertheless, the experiment stations stand before the country as 

 the representatives of agricultural science, manned or presumed to be 

 manned by scientific men. As scientific men Ave should know and 

 should proclaim that permanent progress in agriculture is possible 

 onl}^ through the establishment of principles. One principle well 

 founded is worth a thousand facts, because it includes them all. I 

 can not avoid suspecting that the principles which have been bor- 

 rowed from foreign investigators and popularized by station litera- 

 ture and in other Avays have done quite as much to help the practical 

 feeder as our own experiments. 



But how do matters stand with our borrowed science of feeding? 

 AVill it stand the strain we are putting on it? 



The methods of com])aring the values of feeds and rations which 

 still largely prevail date back almost fifty years to the fundamental 

 investigations of Henneberg and Stohmann at the AVeende Experi- 

 ment Station, in Saxony, begun in 1858 and published in 1800 and 

 subsequent 3'ears. Our methods for the analysis of feeding stuffs, 

 the technic of digestion experiments, and the interpretation of their 

 results, are all, in the main, what were formulated by these investi- 

 gators. They grouped the digestible organic matters of feeding stuffs 

 into pi'otein, fat, and carbohydrates, the latter including the digestible 

 portion of the " crude fiber " and of the '"' nitrogen-free extract,"' 

 and the values of feeds were estimated on the basis of the amounts of 

 these nutrients which they could supph\ 



Henneberg and Stolnnann, howevei-, were fully aware of the fact 

 that such investigation into the content of feeding stuffs constituted 

 but one-half of the problem and tliat it was just as necessary to 

 determine with equal exactness the real nutritive effect produced by 

 their u.se. In 1870, in an introduction to a third report upon their 

 work, Henneberg discussed very fully the methods by which this 

 nutritive effect could be determined, with the aid of the respiration 

 apparatus, on the basis of his familiar conception of the schematic 

 l)ody. Not onl}' this, but he formulated a pi'ogram of systematic 

 investigations and made a beginning in its execution. 



The determination of the digestibility of the nutrients in feeding 

 stuff's, however, could be much more easily and cheaply accomplished 

 than the actual determination of their nutritive value according to 

 Henneberg's program. The assumption of the ecpial \alue of protein, 

 carbohydrates, and fat from different sources having l)een once mad(\ 

 it Avas jierhaps not surprising that the average experimenter should 

 accept this assumption and follow the easier path. Almost innumer- 

 able digestion experiments haxc been made (hiring the last forty-five 



