40 MORPHOLOGY AND CULTURE OF MICROORGANISMS. 



brownian movement is to be sharply differentiated from vital movement 

 which is possessed by some bacteria. 



VITAL MOVEMENT. As already indicated, bacteria have the power of 

 independent movement due to inherent vital power. Only a few of the 

 micrococci are motile, while many of .the bacilli and spirilla are. This 

 movement is a change of position and is caused by certain protoplasmic 

 processes which these bacteria possess, known as cilia (sing, cilium} or 

 flagella (sing, flagellum). The fact of motility or non-motility of an 

 organism is of considerable value to the systematist. It is determined 

 by examination in a hanging drop. At times, however, it varies so little 

 from the brownian movement that it is difficult to tell whether a particular 

 organism or culture does or does not possess vital movement. An opinion 

 can be more definitely formed at times if some chemical producing an 

 anaesthetizing effect on the bacteria is introduced into the examining 

 medium. In case the organism is actually motile its position will be 

 changed or at least in case it is merely a brownian movement there will 

 be no change. 



ORGANS OF LOCOMOTION. The protoplasmic threads referred to as 

 the organs of locomotion are known as flagella, or cilia. The difference 

 between the cilium and flagellum is the fact that a cilium has a simple 

 curve while a flagellum has a compound curve, like a whip lash. Most of 

 the bacteria possess flagella rather than cilia. The size, arrangement, etc., 

 of these flagella are constant and characteristic of a particular organism. 

 Their structure and arrangement, therefore, will be discussed later. 



CHARACTER OF MOVEMENT. Different bacteria present different 

 kinds of movement. Some dart forward with great rapidity, others move 

 slowly; some move in straight lines, others wobble, but any particular 

 character is quite constant and many of the bacteria may be recognized 

 by their characteristic movements. 



RATE. The rate at which the bacteria travel when they possess 

 vital movement varies greatly. Some of them move very fast, others 

 very slowly. Many of them appear to move with wonderful rapidity. 

 Leeuwenhoek, when he first saw these moving bacteria, said that 

 they traveled with such great rapidity that they tore through one another, 

 but it must be borne in mind that under the high powers of the microscope 

 the rate of movement is magnified to the same extent as the object, and 

 that in reality the rate of movement is not excessive. When compared 

 to their size, the rate of movement is probably little greater than that of a 



