10 



SCIENCE 



[Vol. LV. No. 1410. 



have largely failed to meet expectations in 

 establishing correlations between soil treatment 

 and bacterial flora. Such bacteriological ob- 

 servations have now almost ceased in connec- 

 tion with long continued field experiments. 



Reduced to such a simple collection of experi- 

 mental data, the conduct of these extensive field 

 experiments has often become largely a matter 

 of routine. The niceties of plat work are 

 observed, but the element of actual inquiry is 

 deferred until many years have supplied their 

 data. When that time is reached the publica- 

 tion is more often a summary of field and 

 and laboratory records than a critical analysis 

 of the data and their actual meaning. At best 

 the product is quite apt to consist of empirical 

 observations rather than definite contributions 

 to fundamental principles. We have not yet 

 learned how to interpret, except superficially, 

 the answer which the soil and the plant give as 

 to just what has happened or what the ap- 

 ■psa-ent effects are due to. We have not yet 

 learned how to examine a plot of soil so as to 

 determine the changes occurring from time to 

 time or brought about by a long continued 

 system of treatment, or how to connect these 

 changes with the response of the crop in a 

 given season or period. Indeed, relatively 

 little study is now given in such experiments 

 to the soil itself, and only to a limited extent 

 are underlying questions suggested by such 

 experiments being given intensive study. 



In a word, the indications are that in the 

 majority of cases the use is not being made of 

 such long-time field experiments that ought to 

 be made at this stage. They are rarely being 

 simplified as time goes on, with a narrowing 

 down to specific problems for intensive 

 research, and they are not being increasingly 

 supplemented by definitely directed laboratory 

 study. They ought themselves to be progres- 

 sive both in method and outlook. They ought 

 to be used as the source of problems and mate- 

 rial with which to make further and more pro- 

 found inquiries. 



We can hardly fail to recognize the changed 

 status at the present time, both as to practical 

 requirements and the stage which has been 

 reached in research and its problems. What is 

 especially needed at this stage is the study of 

 factors and their relationships rather than 



gross comparisons of one complex of conditions 

 with other complexes. This will call for the 

 kind of team work which has been applied to 

 the Eothamsted experiments, — the association 

 of the chemist and the bacteriologist with the 

 agronomist and soil expert, and the guidance 

 of the statistician in both planning and inter- 

 pretation. 



In many of the feeding experiments, also, 

 the unchecked sources of possible error are too 

 great for safety. The small number of animals 

 in the lots gives large chances for the influence 

 of individual variation. The conditions and 

 frequency of weighing may also give mislead- 

 ing indications. Some of the results of such 

 experiments can be measured quite accurately, 

 while others can only be described. Some are 

 not strictly experimental because they embody 

 so many factors not under experimental control 

 and whose probable variation can not be esti- 

 mated. This is true, as Dr. H. H. Mitchell 

 has recently shown, of the cost or financial 

 returns in feeding. Such results lack per- 

 manent value, and are likely to be given a 

 prominence and an application which they are 

 not entitled to. 



Experiments of this practical type have been 

 useful in the past and there will be need for 

 them in future. It is important that they 

 occupy their proper place; but in the scheme 

 for investigation they should not take the place 

 of nutrition studies based on more permanent 

 factors than prices and food combinations, or 

 reliance rest too largely on them at this stage. 



Many important advancements have been 

 made in animal nutrition which will find appli- 

 cation in feeding practice and in showing the 

 reason back of it. These disclose more clearly 

 the functions to be discharged by food, the 

 inherent qualities which account for the ob- 

 served value or special properties of feeds, and 

 the means of measuring the response of the 

 animal with a high degree of accuracy. Such 

 fundamental investigations ought assuredly to 

 be encouraged, not to the exclusion of but along 

 with the type of feeding experiments which 

 seek a more immediately practical end. 



There is still need to cultivate intelligent 

 public appreciation of research conducted in 

 accordance with the spirit and the method of 



