STRUCTURE OF BACTERIA 



135 



refractile cell wall (e. g., B. tuberculosis and B. 

 anthracis) . 



In some of the higher bacteria the cell wall exhibits 

 this differentiation to a marked degree and forms 

 a hard sheath within which the cell protoplasm is 

 freely movable; and during the process of reproduction 

 the cell protoplasm may be extruded, leaving the 

 empty tube unaltered in shape. 



3. Cell Contents. Protoplasm (mycoprotein) con- 

 tains a high percentage of nitrogen, but is said to differ 



FIG. 85. Diagrammatic sketch of 

 composite bacterium to illustrate 

 details of anatomical structure. 



FIG. 86. Plasmolysis. 



from proteid in that it is not precipitated by C 2 H 6 O. 

 It is usually homogeneous in appearance sometimes 

 granular and may contain oil globules or sap vacuoles 

 (Fig. 85, d), chromatin granules, and even sulphur 

 granules. Sap vacuoles must be distinguished from 

 spores, on the one hand, and the vacuolated appear- 

 ance due to plasmolysis, on the other. 



The cell contents may sometimes be differentiated 

 into a parietal layer, and a central body (e. g., beg- 

 giotoa) when stained by haematoxylin. 



4. Nucleus. This structure has not been conclu- 



