1892.] MICKOSCOPICAL JOURNAL. 3 



Observations on Staining the Flagella on Motile Bacteria.* 



By VERANUS A. MOORE, M. D., 



ASSISTANT IN THE LABORATORY OF THE BUREAU OF ANIMAL INDUSTRY, DEPAKTMENT OF A(;KICULTUKE, 



WASHINGTON, D. C. 



From a microscopical stand point no branch of the investigation of 

 micro-organisms is, perhaps, more interesting than the study of the 

 flagella on motile bacteria. As their discovery has shown the structure 

 of "these organisms to be much more complex than was before sup- 

 posed, the determination of the number and arrangement of these 

 minute appendages with which the various species are provided is im- 

 portant, not only from the knowledge thus derived of their structure, 

 but also as a possible aid in the differentiation of closely allied species. 



The fact that certain motile bacteria were provided with flagella was 

 made known early in the liistory of Bacteriology, but there seems to 

 have been no method devised until a comparatively recent time by which 

 they could be carefully studied or by which their presence on other 

 motile forms could be shown. The difficulty in detecting the flagella 

 on bacteria in a fresh condition is well illustrated by the investigations 

 of Dallinger and Drysdale, who saw only a few of these appendages 

 in a preparation of Bacteriti?n tertfio after an incessant examination of 

 nearly five hours. Although our instrunjents and methods have been 

 much improved since that time I believe that at the present time the 

 satisfactory demonstration of flagella on living bacteria is one of the 

 most diflicult tasks known to microscopists. 



It is through the development of the staining processes that the dem- 

 onstration of these appendages on the great majority of motile bacteria 

 has been made possible, and, in many cases, comparatively simple. As 

 early as 1877 Koch succeeded in staining the flagella on a certain num- 

 ber of the larger saprophytic bacteria. Since then other methods have 

 been devised which are applicable to the smaller and also the patho- 

 genic forms. By the aid of these methods the flagella have become 

 recognized as forming a part in the morphology of motile bacteria. This 

 fact is important, as any difference found to be constant between the 

 characters of the flagella of two bacilli will be as significant in differ- 

 entiating them, the one from the other, as the presence or absence of 

 spores or a difference in the form or size of the bodies of the germs 

 themselves. It is for their differential value that a knowledge of the 

 flagella may render valuable services to the practical bacteriologist. 



In 1SS9 Loefller published a method in which he introduced the prin- 

 ciple of a mordant in staining the flagella and cilia on mico-organisms. 

 By subjecting the preparations to the action of a mordant before they 

 were brought into the staining fluid he succeeded in staining the flagella 

 on a considerable number of bacteria. There were, however, many 

 motile forms on which these appendages could not be detected. This 

 fact led to further investigations, which resulted in the discovery of the 

 principle ^' that the alkali producing organisms required an acid 

 Tnordant and that the acid producing organisms required an alkaline 

 mordant." This was based upon the results obtained by Petruschky,! 

 who had found that a large number of bacteria would convert the reac- 

 tion of a neutral medium (liquid) into either an acid or an alkaline one 

 during their multiplication. 



* Read before the American Society of Microscopibls, August, 1891. 

 t Centralblatt f. Bakieriologie u. Parasitenkunde, Bd. vi (1889), p. 625. 



