132 MICHIGAN STATE AGRICULTURAL COLLEGE 



when he has opportunity true science is none of these things. 

 Some of them may be steps in its direction, but they do not con- 

 stitute "severely tested" or "verified" knowledge. So obvious 

 a truth would scarcely need stating, were it not for the fact that 

 our scientific literature is submerged with increasing records of 

 imcomplete and inconclusive observations. It is a sobering 

 thought that only a minor proportion of the mass of 

 generalizations that are published endures severe scrutiny 

 and becomes permanently incorporated into the body of 

 science. 



Scientific generalizations at their best are far from infallible. 

 Every spot of truth is so surrounded by impenetrated, and there- 

 fore unknown, regions, that many conclusions are properly held 

 to be tentative. Even some deductions, the result of researches 

 apparently most exhaustive, that are stated without reservation 

 or modification, are abandoned as larger knowledge is gained. 

 A most striking example of this is furnished by the investigations 

 as to the sources of nitrogen to the plant. In 1857-58, Lawes, 

 Gilbert, and Pugh carried on at Rothamstead, England, what has 

 been pointed to many times as a classical research on the ques- 

 tion of the use by plants of the free nitrogen of the air. The 

 inquiry was most severe. All available knowledge was brought to 

 bear on it, and the conclusion was reached that uncombined at- 

 mospheric nitrogen is not available plant food. This verdict is 

 now reversed by later evidence of the soundest and most incontro- 

 vertible kind. In 1857 knowledge of the biological activities of 

 the soil was very meager. The Rothamstead investigators worked 

 with sterilized earth, not realizing that they were thus destroying 

 the germ life which, as we now know, somehow functions in 

 aiding the legumes to utilize atmospheric nitrogen. While the 

 plants did not acquire .free nitrogen under the conditions in- 

 volved in the investigation, these conditions were made greatly 

 unlike those prevailing in nature. Science will always be sub- 

 ject to such reversals. Its progress has been, and always will be, 



