1 8 ESSENTIALS OF BACTERIOLOGY 



mm. (=i micromillimeter), written i //. The cell, as other 

 plant-cells, is composed of a membranous cell-wall and cell- 

 contents; nuclei are not found. 



Cell-wall. The cell-wall is composed either of plant cellu- 

 lose, or a form of albumin, since it is less permeable than cellu- 

 lose membrane. The membrane is firm, and can be brought 

 plainly into view by the action of iodin upon the cell-contents, 

 which contract tnem. 



Cell-contents. The contents of the cell consist mainly of 

 protoplasm, usually homogeneous, but in some varieties finely 



Fig. 2. Zobglea. 



granular, or holding pigment, chlorophyl, fat-droplets, and sul- 

 phur in its structure. It permits osmosis, -and is like other 

 plant-cells. 



Gelatinous Membrane. The outer layer of the cell-mem- 

 brane can absorb water and become gelatinoid, forming either 

 a little envelop or capsule around the bacterium or preventing 

 the separation of the newly branched germs, forming chains and 

 bunches, as streptococci and staphylococci. Long filaments 

 are also formed. 



Zobglea. When this gelatinous membrane is very thick, 

 irregular masses of bacteria will be formed, the whole growth 



