24 GENERAL MORPHOLOGY 



it is to control the cell activities, while the space between 

 this body and cell wall is occupied by protoplasm or cyto- 

 plasm, a soft, spongy, or gelatinous matter, which under 

 very high magnification seems to be made up of a delicate 

 meshwork, within the spaces of which a fluid lies. The 

 nucleus is a denser body usually separated from the cyto- 

 plasm by a distinct wall or membrane, and when mashed out 

 is seen to consist of a skein of coarse threads. Into the cyto- 

 plasm the nourishment of the cell passes. Of bacteria, either 

 in their natural condition or stained for examination, only 

 the nucleus and the wall can be seen, the intervening layer 

 being exceedingly thin. 



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a 



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00 



<bo 



c 



FIG. 2. a, staphylococci; 6, streptococci; c, diplococci; d, tetrads; e, sarcinse. 



(Abbott.) : 



In shape, bacteria are either spherical, called cocci (sing., 

 coccus), or straight rods, called bacilli (sing., bacillus), or 

 curved rods, called spirilla (sing., spirillum). Each shape 

 has slight variations, such as the flattening of the sides 

 when two organisms are apposed. The spirilla are, perhaps, 

 subject to more variations than the others, extending from 

 a simple comma shape to that of a long, wavy spiral when 

 looked at from the side. These last are in reality corkscrews, 

 as they twist in three planes. In size microorganisms vary 



