216 STATE BOARD OF AGRICULTURE 



forming a complete organism, it is usually called a vibrio. Thus we speak 

 of the micro-organisms of Asiatic cholera — the vibrio of Asiatic cholera. 

 Classitic-ation: > 



1. Bacillus — bacilli — rod shaped micro-organisms. 



a. Bacterium — short, thick micro-organism. 



2. Micrococcus — micrococci— spherical micro-organism. 



3. Spirillum — spirilla — spiral micro-organisms. 



a. Vibrios — single curved micro-organisms. 



PROTOPLASM. 



The contents of a bacterial cell are normally homogeneous, translucent, 

 and refringent, corresponding closely to the protoplasm, h 

 A earance semi-flaid and almost transparent mass, fqund in other 

 Nnciens Hving cells. So far as known the cell possesses no nucleus; 



still evidences of its existence are present. While the proto- 

 plasm is usually homogeneous, there are conditions when the 

 opposite will prevail. Laboratory workers are acquainted with 

 certain changes in the protoplasm induced by unfavorable mt-dia upon 

 which they grow, by the direct rays of the sun, by a high degree of heat, 

 and by certain chemicals. These agents are artificial. A natural change 

 in the protoplasm occurs when the cell enters the stage of spore produc- 

 tion. The protoplasm will then break up into different sized granules 

 which move towards the center and coalesce. 



CELL WALL. 



The sheath which encloses the protoplasm is of great interest as well 

 as importance. Its composition seems to be that of woody 



Composiiion. fiber, cellulose, as has been established by micro chemists. 



Demonstra- The demonstration of it is dependent largely upon inference 

 tion. aj2(5 analogy. > Owing to certain peculiar arrangements of bac- 



teria and the linking of cells, it does not seem possible that 



such could occur unless the cell be sheathed. Again, by the action of 



iodine, the protoplasm can be made to retract from the cell wall, leaving 

 it behind, unassociated with anything, as a well defined line. 



capsnies. With certain species the cell wall becomes enlarged resembling 

 a gelatinous mass. When this is characteristic of a species, 



it is spoken of as a capsulated micro-organism. The great importance 

 belonging to the cell walls of bacteria is their power to resist 



Resistance. external agents of Hestruction. \Vhile the cell wall of one 

 species will refeist a comparatively high degree of heat or low 



degree of cold, that of another stems to have no resisting power at all. 



Someone may ask whether this power of resistance does not lie in some 



other portion of the cell structure; perhaps it does, but the indications 



lead us to believe that the cell wall is the greatest factor. More light will 



be shed upon this matter as we proceed. At this point a consideration of 



motionaad flagella will be fitti'.g. 



MOTION 



Many bacteria move and their motions differ. One species 

 Kinds. has a tumbling motion through the liquid in whiph it is sus- 



pended, another a darting motion,, and still another a snake- 



