CHAPTER I 



THE MORPHOLOGY OF BACTERIA 



I. THE STRUCTURE OF THE BACTERIAL CELL 



Bacteria are unicellular organisms of the simplest type. A 

 bacterial cell consists of a central body which stains readily with 

 the basic analine colors and other nuclear stains. This central 

 body is surrounded by a capsule of variable form and thickness, 

 but which in the majority of cases is thin and symmetrical. 

 Such a typical cell is shown in Fig. I, B. 



A. The Central Body 



The central body is generally homogeneous in structure, and 

 is only in rare cases granulated. By special staining methods 

 the protoplasm may show a number of deeply colored bodies 

 known as metachromatic granules. These were formerly con- 

 sidered by certain authors as the initial elements of spores, and 

 by others as nuclei. They are now regarded simply as denser 

 aggregations of protoplasmic molecules which possess special 

 staining properties. They are illustrated in Fig. I, B-E. 



According to Migula, in Bacillus oxalaticus, the central body 

 may show the formation of vacuoles, Fig. i, B. Vacuoles are, 

 however, of phenomenal occurrence, and in the majority of 

 bacteria the central protoplasm is homogeneous and dense. In 

 certain species, however, the protoplasm may show unequal 

 staining properties, giving the bacillus a beaded appearance 

 with intervening unstained or feebly stained spaces ; or again, 

 the protoplasm may be aggregated at the poles, with a com- 

 paratively clear central portion. 



