34 VETERINARY BACTERIOLOGY 



Cell Inclusions. Bacterial cells sometimes contain vacuoles, 

 or spaces in the protoplasm filled with sap or some non-staining 

 or non-refractive substance. A large vacuole near the center of 

 the cell may crowd the protoplasm to the ends of the cell, and 

 such organisms, when stained, are said to show polar staining. 

 In other forms, as the diphtheria bacillus, granules are formed 

 that stain much more intensely with the basic aniline dyes than 

 does the remainder of the protoplasm. These are called meta- 

 chromatic granules. The function of these granules is not clear. 

 Certain species of bacteria living in water containing hydrogen 

 sulphid are found to contain granules of free sulphur in their 

 protoplasm. Still others have food materials in the form of oil 

 globules or granules of glycogen. 



Fig. 13. Distribution of the flagella of bacteria: A, Non-motile or atrich- 

 ous bacilli, spirilla, and cocci; B, monotrichous flagella of bacilli, spirilla, and 

 cocci; C, lophotrichous flagella of bacilli and spirilla; D, amphitrichous flagella 

 of bacilli and spirilla; E, peritrichous flagella of bacilli and spirilla. 



Flagella. Many bacteria are motile by means of whip-like 

 threads of protoplasm which extend from their surfaces. These 

 threads are known as whips or flagella (sing, flagellum). These 

 flagella are observed with difficulty in the living organism ex- 

 cept with dark field illumination and require peculiar stain- 

 ing technic and careful treatment to make them visible in a 

 stained mount. Comparatively Jew cocci, many of the bacilli, 

 and most of the spirilla are flagellated. The distribution of 

 flagella on the surface of the cell has been used as a basis for 

 grouping. Atrichous bacteria have no flagella; monotrichous 

 bacteria have a single flagellum at one end; lophotrichous, a group 

 of flagella at one pole; amphitrichous, flagella at both ends; and 



