HISTOLOGY OF THE CILIA 39 



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 tetragenus 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, eg. in Chromatium or in tufts, the latter- 

 consisting, in the case of Bacterium termo, 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 distri- 

 butive 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.) proposed the same method for readily differentiating Bacterium 

 coli commune from Bacilhis typhi abdominalis, which is very important in the 

 bacteriological examination of water. He found the former microbes to be pro- 

 vided with at most three cilia apiece, whereas the bacillus had from eight to 

 twelve. Subsequently, however, it was ascertained by FEBRIER (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 obtained the individual cells of 

 which exhibit as many as ten cilia ; by this determination, therefore, the system 

 of Messea, as also the hopes of Lukscb, were deprived of support. Moreover, 

 Messea had been forestalled, as in 1864 DAVAINE (I.) proposed to separate the 

 fission fungi into two groups ; the one, forming his genus Bacteridium, comprised 

 all the species in which he could not detect independent movement under any 

 circumstances ; whilst the others, his genus Bacterium, included all the motile 

 species. In J. Schroeter's work (published in 1870) on pigment bacteria, of 

 which a notice is given in a subsequent section, this method of classification was 

 adopted, but later workers have abandoned it, and the term Bacteridium is now 

 perfectly obsolete. 



When a bi-polar ciliated bacillus divides in two in the act of reproduction, 

 the new-formed poles are, naturally, without such locomotive organs at the 

 outset, but they quickly develop, and thenceforward each of the two cells is 

 ciliated at both poles. That these organs are extremely minute need not be 

 emphasised. Frequently they are undetectible by the ordinary means of 

 observation, even with objectives of the highest power and clearest definition, 

 since it is difficult to see the cilia, not only because of their extreme minuteness, 

 but also because their refractive power is almost the same as that of the liquid 

 in which they are immersed. In order to make them more readily recognisable, 

 use is made of the special methods cf staining devised by LOEFFLEK (I.). Some 

 directions relative to these will be found in UNNA'S (I.) historic-critical review 

 of the development of bacterium-staining, drawn up in 1888, and continued by 

 L. HEIM (I.) up to the year 1891. Plate I. shows four photographs of motile 

 bacteria taken by Loeffler from preparations stained in this way. 



40.-Histology of the Cilia. 



This subject has hitherto received little attention. Van Tieghem considered 

 the cilia to be gelatinous elongations of the cell envelope, and their movement 

 as merely passive, the locomotive power being ascribable to contractions of the 

 plasma in the cell. He found that the cilia of Clostridium butyricum gave the 



