THE FLAGELLA OR CILIA. 49 



the first of which is occasioned by alternate contraction and re- 

 expansion of the plasma canal. This kind of movement occurs in 

 the case of such thread bacteria as attach themselves to a support 

 by one of their poles, and then swing with a pendulous motion 

 from this point of suspension, either remaining in the same plane 

 the while or describing a cone. 



39. The Flagella or Cilia. 



Much more frequent is the second or roving movement, 

 noticeable in free unattached bacteria, and produced by special 

 locomotive organs termed flagella or cilia. These were first 

 noticed by EHRENBERG (L), in 1836, in a spirillum which he 

 discovered in a brook near Jena, and named Opliidomonas 

 jenens/'s. Closer attention was first bestowed on these organs by 

 COHN (L). 



VAN TIEGHEM (I.) was of opinion that these locomotive organs 

 were peculiar to bacilli ; but similar locomotive powers were at a 

 later date observed in the cocci, such as the Micrococcus tetra- 

 yenus mobilis ventriculi, discovered by MENDOZA (I.) in 1887 ; the 

 Micrococcus agilis, found by ALI-COHEN (I.) in 1889; a coccus 

 (unspecified) studied by LOEFFLER (II.) in 1890; later, the 

 Micrococcus agilis citreus of MENGE (I.) ; and finally, the Sarcina 

 mobilis of MAUREA (I.). 



The position of these organs in the bacilli is either polar or 

 lateral. The polar flagella are either single as, e.g. in Chromatium 

 or in tufts, the latter consisting, in the case of Bacterium termo y 

 of three or four, and in various spirilla of eight to twelve, cilia. 

 In Spirillum undula they are often plaited into the form of a 

 queue. The lateral cilia are, as was found by A. FISCHER (II), 

 evenly distributed over the entire surface of the bacterial cell, 

 their number being given by Loeffler as twelve in the case of the 

 typhus bacillus. 



Starting with the assumption that the number of the cilia 

 and their distributive arrangement on the cell are constant for 

 each kind, A. MESSEA (I.) endeavoured to make this character 

 the basis of a classification of the bacteria. L. LUKSCH (I.) pro- 

 posed the same method for readily differentiating Bacterium coli 

 commune from Bacillus typhi abdominalis, which is very im- 

 portant in the bacteriological examination of water. He found 

 the former microbes to be provided with at most three cilia apiece, 

 whereas the bacillus had from eight to twelve. Subsequently, 

 however, it was ascertained by FERRIER (I.) that the number, 

 form, and length of the cilia depend on the conditions of the 

 culture. From the bacterium in question cultures can be ob- 

 tained the individual cells of which exhibit as many as ten cilia ; 

 by this determination, therefore, the system of Messea, as also 

 the hopes of Luksch, were deprived of support. Moreover, 



VOL. I. D 



