1891.] MICROSCOPICAL JOURNAL. 15 



A Review of the Methods of Demonstrating the Flagella on Motile 

 Bacteria with Special Reference to the Staining Processes.* 



By VERANUS A. MOORE, M. D., 



ASSISTANT IN THE LABORATORY OF THE BUREAU OF ANIMAL INDUSTRY, DEPARTMENT OF AGRICULTURE, 



WASHINGTON, D. C. 



There is, perhaps, no element in the known structure of micro-or- 

 ganisms that is more difficult to demonstrate than the flagella of motile 

 bacteria. Ehrenberg was among the first of the earlier investigators in 

 this field to infer from the discovery of a vortical action in front of a 

 large motile spirillum {S. volutans) that its movements were pro- 

 duced and controlled by a pair of fine flagella, one at each end of its 

 spiral body. With the improved microscopical apparatus, Cohn (i) 

 succeeded in demonstrating the presence of the supposed flagella on this 

 spirillum, and his discoveiy was confirmed shortly afterwards by Dal- 

 linger, Drysdale, and others. This fact suggested the idea that all 

 motile bacteria depended for their movement on similar motile fila- 

 ments. 



Dallinger and Drysdale (2), basing their work upon the fact that 

 the minuter monads are provided with one or more flagella, turned 

 their investigations to Bactcrhiiu ter7}io to determine whether or not 

 there existed a flagellum or flagella on that bacterium. For this work 

 a 1-16 inch Powell and Lealand immersion lens was employed, and 

 special care taken to secure the best possible illumination. The speci- 

 men examined was prepared by adding a bit of culture of the bacterium 

 termo grown in Cohn's nutritive fluid to a drop of distilled water on a 

 slide and covering it with an extremely thin cover-glass. The exam- 

 ination was continued incessantly for nearly five hours, ^vhen a flagellum 

 was distinctly seen at one end of each of two termo that were moving 

 slowly across the field. The flagella, as seen on the moving germs, 

 were exquisitely delicate and constantly lashing. Other large motile 

 bacteria were subsequently found to possess similar flagella. 



The difficulty in detecting the flagella on motile bacteria in a fresh 

 condition is well illustrated by the above briefly-described experiment. 

 It is also a fact worthy of note that the flagella have been seen by this 

 process only on the larger saprophytic forms, and that the smaller and 

 especially the pathogenic germs could not be considered as possessing 

 flagella, except from analogy, until other methods had been devised. 



Dr. R. Neuhauss (5) reports a successful demonstration of the flagella 

 on the comma bacillus by means of photography. A culture of this 

 bacillus in meat broth was allowed to grow for four weeks, when it 

 showed, instead of the ordinary delicate comma bacilli, large, thick 

 bacilli and long spirilla. Most of these had lost their motility, but a 

 few germs were still capable of movement. A preparation was made by 

 adding a small quantity of this culture to a drop of distilled water on a 

 slide and covering it with a thin cover-glass. In this condition they 

 were photographed, and a negative obtained which showed a delicate 

 spiral flagellum attached to a short, much-curved bacillus. Other suc- 

 cessful negatives were also obtained from the same field by focusing. 



It is, however, through the development of staining methods that 

 the demonstration of these hair-like appendages on the great majority 



* Read before the Washington Microscopical Society, February 20, 1891. 



