The Character of the Flagella 341 



has appeared to be the most trustworthy, although its appli- 

 cation to the different species of bacteria has been attended 

 with much difficulty. It has frequently happened, even 

 when the method was apparently strictly adhered to, that the 

 outcome has been absolutely negative, while in other in- 

 stances the result would be entirely satisfactory. 



Since the description of the original methods the literature 

 on this subject has been exceedingly meager. In a commu- 

 nication to the American Society of Microscopists'', in 1891, I 

 pointed out several of the difficulties usually experienced in 

 the application of I^oeffler's method, and suggested certain 

 modifications, more especially in the technique, which I had 

 found would to a great extent overcome these objections. In 

 the same paper it was also stated that the principle laid down 

 by LrOefBer ' ' that an acid* producing germ required an alka- 

 line mordant, and an alkali producing organism an acid mor- 

 dant," need not be taken in a strict sense, as the flagella on 

 certain of the acid and of the alkali producing bacteria could 

 be stained by the use of either a neutral, acid, or alkaline 

 mordant. 



Straus" has recently reported a very simple methodf by 

 which he could stain the flagella on certain living bacteria. 

 The process has given in my hands universally negative 

 results. 



lyuksch'" has modified Loefiler's method principally by 



*In 1890, Dr. Theobald Smitii {Ceiitralblatt f. Batiteriologie u. Para- 

 sitenkunde VIII, (i8go), p. 389) pointed out the fact that liquid cultures 

 of certain bacteria would be acid or alkaline, according as glucose or 

 other sugars were present or absent. These undergo fermentation with 

 the formation of acids. In liquids free from sugars the reaction re- 

 mains alkaline. (See his paper in this volume.) Petruschky's (Ibid, 

 VI, 1889) classification of bacteria as acid or alkaline producing is 

 thus shown to depend largely on the presence or absence of carbo- 

 hydrates in the culture medium. 



t The method is as follows : To a hanging drop preparation of the 

 culture a drop of staining fluid consisting of carbol fuschin one part, 

 and distilled water three parts, is added and the preparation examined 

 at once. He states that the moving flagella can be observed for about 

 15 minutes. 



