Cell-Wall of Bacteria 



27 



The cell-ivall and its cnntents. — It is not known exactly 

 what substance or substances enter into the composition 

 of the cell-wail. In some cases, cellulose seems to be 

 the main con:;tituent. In the majority of cases, however, 

 cellulose does not seem to be present^ but, rather, a 



Fig. 11. Microscope and accessories for bacteriological work. 



horny, chitinous matter, the elements of which are 

 as yet unknown. 



Inclosed within the cell-wall is the protoplasm, a 

 semi-fluid protein substance which is the seat of the 

 chemical changes produced within the cell. The living 

 force in the protoplasm provides for the building up and 

 the tearing apart of chemical compounds, for the pro- 

 cesses of assimilation and decomposition. 



Content of the protoplasm. — The protoplasm of some 

 species is characterized by its content, glycogen, a kind 

 of sugar — found also in the human liver. Glycogen is 



