28 BACTERIA. 



has many points of resemblance to the mucine found in the 

 tissues, especially the embryonic tissues of animals. This 

 capsule of the B. anthracis, unlike myco-protein, contains 

 no sulphur, is soluble in dilute alkalies, but insoluble in 

 water and acetic acid. 



Dallinger some time ago pointed out that at each pole of 

 an organism which he had studied most thoroughly (the Bac- 

 terium termo, a small oval organism not now recognized 

 as a species) there was developed an extremely delicate 

 flagellum which, he assumed, had something to do with 

 propelling the organism through the fluid in which it 

 was growing, as this organism exhibited most active move- 

 ments in such fluid. As a considerable number of other 

 organisms also possess this same motion in fluid media, it 

 was argued that as in the case of the above organism and 

 of other cells that have an extreme degree of motility, 

 there would also be found flagella or cilia such as are 

 met with in the swarm cells of certain algae, where cilia 

 or flagella are continued directly from the protoplasm, 

 through the cell membrane, if present, and so to the out- 

 side of the organism. Although the existence of these 

 flagella was suspected in many bacteria, they could actually 

 be demonstrated in the case of some of the larger organisms 

 only. Now, however, the number of bacteria in which flagella 

 have been seen has been gradually but surely increased, and 

 lately Loffler has described and photographed most exquisite 

 lash or thread-like filaments, single or in little groups, in 

 Koch's cholera bacillus, in the bacillus associated with the 

 causation of typhoid fever, and in a considerable number 

 of other motile bacteria. 



Whether these cilia and flagella are developed from the 

 protoplasm of the organism, or whether they are merely 

 secondary modifications of the external membrane, remains 

 as yet a doubtful point. It is quite possible that in many, 

 even of the motile forms, flagella are entirely absent ; the 

 organism in such case relying for its motile power on con- 

 traction of the protoplasm within an elastic or not too 

 rigid membrane. In a straight rod-like organism an un- 

 dulating movement may often be observed, whilst both 

 rotary and undulating movements are met with in spiral 

 organisms, though these latter are very frequently supplied 

 with well-formed flagella. It is possible that in certain species, 



