August 27, 1915] 



SCIENCE 



259 



verified by Schloesing and Miintz, who by 

 inhibiting the function of bacteria by means 

 of an antiseptic found that nitrates failed 

 to be produced, but, without the antiseptic, 

 nitrates formed normally. This was many 

 years before Winogradski isolated the 

 organisms. However, with the finding of 

 the organisms, it became possible to ascer- 

 tain the conditions under which they oper- 

 ate most energetically, thus establishing con- 

 trol. This resulted, of course, in the addi- 

 tion of intelligent and valuable practises. 

 Recapitulating, therefore, for the purpose 

 of illustrating a single scientific develop- 

 ment and sequence over a comparatively 

 short period of time, it may be categorically 

 stated that Liebig recognized nitrification 

 in the soil; Pasteur's mind and hand fur- 

 nished the general principle, fermenta- 

 tion, and suggested that this change in soil 

 may be due to microorganisms; Schloesing 

 and Miintz demonstrated the truth of 

 Pasteur's suggestion by the use of anti- 

 septics, and "Winogradski completed the 

 task by the isolation of the organisms and 

 the study of their nature. 



No more interesting scientific fact can 

 be found than the culmination of centuries 

 of observations and speculation in the 

 classical experiments of Hellriegel and 

 Wilfart. The accumulation of nitrogen 

 in the soil had assumed a reality, even in 

 Liebig 's time, and the value of legumes to 

 soil fertility was mentioned by Pliny, but 

 it remained for Hellriegel and "Wilfart to 

 relate these facts definitely through the 

 microorganisms in the nodules of legum- 

 inous roots. Symbiotic fixation of nitrogen 

 materialized. A new era was introduced 

 for practise, since with the isolation of the 

 organisms by Beijerinck two years later it 

 became possible to demonstrate directly the 

 absorption of atmospheric nitrogen by the 

 nodule microorganisms and further to em- 

 ploy them advantageously in the inocula- 



tion of plants, until to-day many thousands, 

 of cultures are utilized in the course of a 

 year. If our purpose were mercenary, it 

 could easily be calculated that millions of 

 dollars were added to the wealth of the 

 United States without the exhaustion of 

 any resource. Man's power has increased 

 a hundredfold in this particular alone. It 

 may be safely said that it has already meas- 

 ured to this estimate and its possibilities 

 are still open. 



Symbiotic fixation of nitrogen must not 

 be confused with the non-symbiotic. As 

 late as 1885 Barthelot determined the pres- 

 ence of microorganisms in the soil which 

 without association or symbiosis with the 

 plant possessed the power of accumulating 

 nitrogen. In the soil this nitrogen appears 

 available for plant nutrition. "While this 

 means of gathering nitrogen may appear 

 pregnant with future inducements, as yet 

 its values are illusive, for little headway 

 has been made in transforming the intrinsic 

 energy into forms of great usefulness. This: 

 should not, however, be cause for discour- 

 agement, for like the discovery of oxygen, 

 its ramifications are its future for man. 

 Projected applications can not be measured 

 by a score of years, but by centuries, not 

 by present attainment, but by future 

 progress. 



The activities of microorganisms in the 

 soil do not stop with the decomposition of 

 nitrogenous organic matter resulting 

 through oxidation in nitrification and per- 

 haps later in denitrification or in the 

 symbiotic and non-symbiotic fixation of 

 nitrogen, for with the fermentation of the 

 ternary compounds there are produced such 

 substances as carbon dioxide and other 

 organic acids which act directly or in- 

 directly upon the mineral constituents and 

 in this manner furnish food for plant 

 growth not otherwise available. Then too 

 there are the sulphur and iron bacteria 



