and Laboratory Methods. 



1917 



Influence of Light in Pigment Production of Bacteria. 



In his Manual of Bacteriology, 1892, Sternberg observes that when Bacillus 

 mycoides roseus is grown " upon the surface of agar, in the dark, a pink layer 

 is developed, while in the light it is white." A similar statement is made by 

 Schenk. Crookshank also observes that this bacillus, in the absence of light, 

 produces a pink growth on agar ; while McFarland refers to it as an example 

 of bacteria which produce their pigments only in the dark. A number of other 

 authors have been consulted, including Lehmann and Neumann, Lafar, Novy, 

 Park, Abbott, Williams and Chester without finding any further mention of the 

 matter. No author has been found who disagrees with those quoted, yet with 

 the culture in my laboratory, which was obtained from a well-known and reliable 

 government laboratory, and which appears in every other way perfectly typical, 

 I have obtained diametrically opposite results. As these results are uniform, 

 and have been observed year after year for a number of seasons, it seems desir- 

 able to call attention to the matter, since if my observations are correct many 

 are being erroneously taught in this regard. 



For the purpose of demonstrating to my classes the influence of light in the 

 production of pigment by bacteria, it has been my practice to place chromogenes 

 on similar media in an east window and duplicate cultures in a dark closet sepa- 

 rated from the window only by the thickness of the boards of which the closet is 

 constructed, the conditions as to temperature, etc., being identical. The result, 

 with Bacillus mycoides roseus, on agar streak cultures, whether in warm or cold 

 weather, has been to obtain a pale, yellowish red to rose color in the dark closet, 

 and a deeper shade of a more brilliant hue and a more abundant pigment pro- 

 duction in the parallel cultures in the window. On gelatin, which is slightly 

 liquefied, the color in the window is still deeper than that on agar, reaching, after a 

 few weeks' growth, a rich crimson. The latter medium has only been tried in win- 

 ter, as it would be melted if thus exposed to the heat of the sun in summer. 



Howard University. W. W. AllEGER. 



A Simple Form of Dropper for Use in Cutting Celloidin 



Sections. 



A very convenient " dropper " for keeping the 

 knife flooded with alcohol while cutting celloidin sec- 

 tions may be made, in a few minutes, from a 500 c. c. 

 Florence flask and an iron tripod. The apparatus 

 shown in the figure is so simple as hardly to need ex- 

 planation. The tube D, which is drawn to a narrow 

 opening at its lower end, must be, of course, a little 

 longer than the tube C, to produce siphonal flow. The 

 rapidity of flow is regulated by the screw-clamp B on 

 the rubber connection. The weight of the alcohol in 

 the flask will permit its being inclined at any desired 

 angle, and, by having the tube C too short to reach 

 the bottom of the flask, the flow of alcohol will cease while there is still enough 

 of it left in the flask to prevent overturning. To start the flow, it is only neces- 

 sary to blow into the tube A, as in an ordinary wash-bottle. 

 Allegheny College. A. M. ReesE. 



