496 



SCIENCE. 



[N. S. Vol. XXI. Xo. 535. 



Full paper to be printed in the Journal 

 of Infectious Diseases (with G. E. "NYill- 

 eomb). 



A Simple Method for Determining the 

 Ability of Bacteria to Ferment Different 

 Sugars: L. A. Rogers, U. S. Bureau of 

 Animal Industry. 



In volume VII., page 241, of the Cent, 

 f. Bakteriologie, 2d Abt., Linder describes 

 a simple method for the determination of 

 the ability of yeasts to ferment different 

 sugars. This method consists essentially 

 in filling the cavity of a concave glass with 

 sterile water, inoculating with yeast, add- 

 ing a very small amount of the sugar and 

 sealing on a cover glass. The fermenta- 

 tion of the sugar is indicated by the ap- 

 pearance of bubbles under the cover-glass. 



AYith a few minor variations this 

 method may be used with bacteria. For 

 this purpose litmus is added to sugar-free 

 bouillon until it has a deep blue color.. 

 The sugars to be tested are made to a 

 syrup and sterilized in small phials. The 

 slides and cover-glasses may be sterilized 

 in Petri dishes. A single tube of the 

 litmus boiullon is inoculated with the or- 

 ganism to be tested and incubated for a 

 few hours. A ring of vaseline is run 

 around the cavity of the slide while it is 

 warm and the cavity completely filled with 

 the culture. A loopful of the sugar solu- 

 tion is added . to each and a cover-glass 

 placed carefully over the cavity and 

 pressed onto the vaseline without admitting 

 any air bubbles. The surplus media may 

 be taken up with a filter paper. After a 

 period of incubation the fermentation of 

 the different sugars will be indicated either 

 by the appearance of gas bubbles or by the 

 reddening of the litmus, or by both. 



The advantages of this method over the 

 ordinary fermentation tubes are the rapid- 

 ity with which the fermentation of a large 

 .number of sugars may be determined and 



the veiy slight expense required for the 

 sugars. 



"With the fermentation tube the expense 

 of determining the fermentation of the 

 rarer sugars is so great that the fermen- 

 tative ability of an organism is ordinarily 

 given for three or four sugars. 



With the culture-slide method the 

 amount of sugar used is so slight that a 

 small amount may be kept always ready 

 for use, thus obviating the necessity of 

 keeping on hand a large number of differ- 

 ent kinds of media. The danger of con- 

 tamination may seem a serious obstacle, 

 but with ordinary care it is very slight 

 and may be reduced to a minimum by the 

 use of a case for the protection of the slides. 

 A convenient arrangement for this purpose 

 is a box with glass sides made after the 

 pattern of a balance case, with a sliding 

 door so that the slides may be prepared 

 with only the forearms inside the case. 



.1 Simple Method of Cultivating Anaerotic 



Bacteria: B. R. Rickards, Boston Board 



of Health Laboratory. 



AVith solid media, an ordinary inoculated 

 slant or stab tube immersed mouth down 

 in a receptacle containing alkaline pjTO- 

 gallic acid is used. Plates are made by 

 using an Erlenmeyer flask instead of a 

 Petri dish, inverting and immersing as 

 with tubes. 



For liquid media, the Lawrence form of 

 fermentation tube is used, the liquid being 

 allowed to run into the closed ann before 

 inverting and immersing the mouth of the 

 tube in the pyrogallic acid. 



{Cent. f. Bait., Orig. XXXVI., s. 557.) 



Xew Apparatus: H. W. Hill, Boston 



Board of Health Laboratory. 



Porous Top for Petri Dishes.— The 

 porous top is an exact duplication, in 

 porous flower-pot earthenware, of the ordi- 

 nary glass top, and is used in every way 



