X. THE CHANGE OF PROTOPLASM STRUCTURE 307 



On studying the X-ray diagrams of bacterial flagella, Astbury (146) 

 has found that films produced from the flagella show fine a-keratin 

 reflection and, upon squeezing, this goes over into the /5-keratin pattern. 

 Since it is known that a-keratin pattern is formed when keratin 

 molecules are expanded, while /9-keratin pattern is revealed when the 

 molecules are contracted, it is obvious that the movement of the fla- 

 gella is brought about by the extension and contraction of the protein 

 molecules. 



However, whether or not the movement of flagella can lead to 

 the movement of the bacteria themselves is another question. The 

 writer holds the opinion that bacterial movement is not brought about 

 by the flagella, but that bacteria can move by making use of the 

 thermal motion of water molecules. As is well known bacteria show 

 a very active Brownian movement which is caused by the bombard- 

 ment of water molecules in thermal motion, it should therefore be 

 expected that bacteria will be able to move in a definite direction if 

 they have a specific form by which the bombardment of water mole- 

 cules become effective only in one direction. It may not be difficult 

 for bacteria to acquire such a form. Presumably flagella act as rodders 

 and perhaps, in addition, play a role in making effective the energy 

 of the water molecules. It is inconceivable that contraction and 

 extension of the flagella, only frail bands of protein molecules, result 

 in the active movement of the bacteria. 



In this connection, it should be noted that pijper (147) claimed that 

 bacterial flagella are not the locomotive organs of the bacteria, but are 

 merely mucous twirls trailing from the cell surface. It seems, however, 

 possible that the flagella themselves can achieve some motion and have 

 some connection with the bacterial movement, and so it seems more 

 reasonable to consider that though bacteria do not move by flagella, 

 flagella contribute to the movement. 



The writer has reached such a conclusion mainly from an obser- 

 vation on a kind of bacteria, perhaps a strain of water vibrio, which 

 accidently contaminated a protein solution stored in an ice box. This 

 strain of bacteria could vigorously proliferate at the low temperature 

 in ice box, and move very briskly in a definite direction at a full speed 

 as if flying in the air. Under the microscope of dark field illumination 

 the speed appeared to have no connection with the temperature ; they 

 moved in icy water apparently at the same velocity as in water of 

 laboratory temperature. If the movement is raised by flagella composed 

 of protein molecules being enabled to move by the interposition of 

 lipids, it should be very sensitive to environmental temperature just 

 as the movement of cold-blooded animals. On the contrary, if the 

 thermal motion of water molecules is directive, the temperature 



