PROBT.EMK IN ANIMAL NUTRITION. 517 



AtAvator bomb — not to say the heavy artillery of respiration ap- 

 l^aratus and (•ah)rini('ter. The slino- niay still jirove a formidable 

 weapon, if wielded by tlie hand of a David, and the smooth pebbh' 

 from the brook may still do its wonted exeention. It is largely a 

 question of aim. 



"^riie disc()\-ery and estal)lishment of natural })rinciples and laws 

 recpiire the rigorous methods of physical and chemical research. 

 By this path alone can we hope to attain a clear and definite (juanti- 

 tative conception of the ])rocesses of nutrition. J>ut this alone is no 

 more sufficient than the i)ractical feeding experiment. AVe are deal- 

 ing with an applied science, and our task is only half conii)leted 

 when we luixc established the funthimental principles of nutrition. 

 We are under an e(pial obligation to show how these principles apply 

 to the practical j)i'()blems of feeding, and for this purpose nothing 

 can take the i)lace of actual experiments under the conditions of 

 practice. If our i)ractical experiments in the past have not been 

 fruitful of general results it is not because they have been practical, 

 but rather because they have not l)een so in the best sense. Tn too 

 many cases they have lacked aim. They have not been informed by 

 that comprehensive view of the whole subject which constitutes the 

 essence of science, and so. addressing themselves to petty temporar}' 

 or local questions, have, while admirable in their technical detail, 

 failed to materially advance our knowledge. The more thorough 

 and exhaustive our scientific studies of nutrition become, the greater 

 will lie our need for correlated practical exiieriments, scientifically 

 planned to answer definite questions regarding the aj^plicatioii in 

 practice of the principles worked out in the laboratory or the respira- 

 tion apparatus. 



While this paper was in course of preparation. I received, from one 

 of the leading investigators in animal husbandry in this country, a 

 letter containing a number of inquiries regarding certain points in 

 animal nutriticm. If designed to reveal my limited knowledge of the 

 subject, the letter was an uncjualified success. To nearh^ all the in- 

 quiries I was compelled to return either conjectures or a simple '' I 

 don't know." I was, however, greatly interested in the letter from 

 two points of view. In the first place, it illustrated the possibility 

 of which I have just been speaking, namely, securing results of gen- 

 eral value from practical experiments. The investigations which this 

 gentleman has been carrying on have related primarih' to questions 

 of practice, yet he has been able to plan his experiments and study 

 his results so as to give tht^m an important bearing upon certain ques- 

 tions regarding the principles of nutrition. In the second place, the 

 letter illustrates the inadequacy of the practical experiment alone and 

 the necessity for scientific investigation along parallel lines. His ex- 

 periments and experience raised questions which could not possibly 



