SOURCES OF KNOWLEDGE 203 



widely and persistently held it is not altogether with- 

 out reason or foundation. It is often the expression, in 

 more or less correct terms, of some important principle. 

 No one should lightly turn aside from widespread tra- 

 ditions and convictions in regard to any line of practice. 

 A knowledge of the precepts governing the feeder's art 

 that are the accumulation of experience in the care of 

 animals is to be respected and is, to a great extent, essen- 

 tial to successful practice. It is also true that little sub- 

 stantial progress can be realized in any art if its under- 

 lying truths are not understood, for when this is the case 

 the results of experience under one set of conditions do 

 not serve as a guide under circumstances entirely different. 



290. Practical feeding experiments. With the advent 

 of modern science and of the efforts to utilize it in agri- 

 culture, an attempt has been made to search for impor- 

 tant truths more systematically, an effort undertaken 

 chiefly by experiment stations. As one means of gain- 

 ing knowledge, these institutions, and to some extent 

 private farmers, have conducted many so-called practical 

 feeding experiments in order to verify present beliefs, 

 test theories, and solve existing problems. The relative 

 value of various feeding-stuffs and rations for producing 

 growth and milk and the influence of different fodders 

 and grain foods upon the quality of the product have 

 been the subjects of numerous feeding tests. Much 

 valuable information has been secured in this way, but 

 there has not always been a full recognition, even by 

 experiment stations, of the limitations which should be 

 observed in drawing conclusions from this manner of 

 experimentation. 



291. Inconclusiveness of ordinary feeding experi- 

 ments. In order to view this matter more in detail, let us 



