SIZE AND STRUCTURE OF THE BACTERIAL CELL. 37 



the flagella are merely projecting threads of protoplasm it 

 might be expected that in plasmolysis they would be with 

 drawn within the cell and that motion would cease. This, 

 however, is not the case. The plasmolyzed living cell 

 continues to move the same as in the beginning. The 

 flagella, therefore, are not directly connected with the inner 

 protoplasm of the cell. They are given off by the cell-wall 

 and chemically they would seem to be identical with the 

 outer, softened layer of this structure. 



As indicated above, the cell-wall is essentially protein 

 matter and, unlike the cellulose wall of higher plant cells, 

 it takes an active part in the life of the cell. The cell-wall 

 receives its nourishment from the protoplasm and is itself, 

 therefore, a living structure. The filaments or whips given 

 off by the outer layer of this wall are also protein in nature 

 and are also living. The flagella are unquestionably the 

 organs of motion. By inducing movements in the liquid 

 they renew continually the food supply. Moreover, it is 

 possible that the protoplasmic whip is a means of absorb- 

 ing nourishment for the cell. In the latter case it might be 

 expected that flagella would also be present on non-motile 

 bacteria. Flagella, however, are never found on strictly 

 non-motile organisms. Pseudo-flagella, due to a mucous- 

 like secretion, are sometimes met with in such cases. 



The arrangement of flagella on a given species is fairly 

 constant, but will vary with different species. In the vibrio 

 of Asiatic cholera, and in the bacillus of green pus, there is 

 usually only one whip present and that is attached to one 

 end. At times, the cholera vibrio may have two, three or 

 four whips at one pole, and again it may have none. In 

 old cultures it may have a whip at each end (Fig. 6 d). 



The spiral forms, as a rule, have a bunch of whips at 

 one end. When each end is equipped with a bunch of 

 whips it is because there are really two cells present. The 

 whips on the spiral forms are not as flexible and wavy as 

 those on the bacilli. They appear rather stiff and are 



