229G Journal of Applied Microscopy 



CURRENT BACTERIOLOGICAL LITERATURE. 



H. W. CONN, Wesleyan University. 



Separates of Papers and Books on Bacteriology should be Sent for Review to H. W. Conn, 

 Wesleyan University, Middletown, Conn. 



,, . ^. . . ., . , ^ . r, . , „ The author gives an instance of a 

 Kunn. Die Assimilation des frien Stickestortes ° 



durch Bodenbakterien ohne Symbiose mit very practical demonstration of the 



Leguminosen. Fuhlings Landw. Ztg., p. 2, importance of nitrogen assimilating 

 I90I. ^ ° ° 



organisms in the soil, independent of 



the action of legumes. It consists of observations made upon an experimental 



plot in the Agricultural Institute of Halle. For twenty years this plot has been 



under cultivation, producing every year the same crop. A study of the harvest 



has shown that there has been, practically, no diminution in the harvest, and that 



the amount of combined nitrogen in the harvest and soil has not diminished as 



the result of the twenty years cultivation. Inasmuch as no legumes were 



planted in the soil during the whole period and there was no diminution in fixed 



nitrogen, the author concludes that it must be because there are present in the 



soil some agencies, probably micro-organisms, which assimilate free atmospheric 



nitrogen. h. w. c. 



Winslow, C. E. A. Color Standards for Re- The Study of the effect of external con- 

 cording the Results of the Nitrate and Indol ditions upon B. coli conimiDlis has em- 

 Tests. Inst, of Techn., Boston, Mass. , • 1 , ^ r ^•r^ 



phasized the need of some dmerent 



standard by which the capacity of the bacteria to produce nitrate and indol can 

 be quantitatively measured. Even when the conditions of experiment are 

 rigidly controlled, striking variations sometimes appear, and the law of such 

 variations can be properly studied only when the results are carefully compared 

 with each other. 



The use of a color standard for measuring the reduction of nitrate and the 

 formation of indol obviously suggests itself as simple and more practical than 

 any other. 



Up to the point at which a precipitate forms in the nitrite reaction, the depth 

 of color in both cases may be considered as roughly proportional to the amount 

 of the end product formed by the bacteria in a given time. The problem for the 

 bacteriologist is, then, to select from the numerous schemes of color values pre- 

 pared for artistic and educational purposes that one best suited for the matching 

 of the reaction in question. 



The most rational system of color standards which has come to my notice is 

 that prepared by Milton Bradley, of Springfield, Mass., based on pure spectral 

 colors of known wave length. It is issued in the form of a small booklet, and 

 by cutting out and pasting to a card the colors between Red and Yellow Orange 

 and their tints, a chart is obtained on which the color of the indol reaction pro- 

 duced by B. coli communis can be readily matched. The hue is read by holding 

 the tube parallel to a white surface and looking through it at right angles, while 



