GENERAL MORPHOLOGY 25 



homogeneous, possessing a very low power of refracting 

 light. They consist of nucleus, cytoplasm, and a wall 

 which is probably a simple superficial condensation 

 of the protoplasm. The ordinary animal or vegetable 

 single cell 1 contains an easily distinguishable body, 

 usually central, called the nucleus, whose function it 

 is to control the cell activities, while the space between 

 this body and cell wall is occupied by protoplasm or 

 cytoplasm, a soft, spongy, or gelatinous matter, which 



9 S 



V D D * 

 M CP <f> (f 



FIG. 2. a, staphylococei; b, streptococci; c, diplococci; d, tetrads; 

 e, sarcinae. (Abbott.) 



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 cytoplasm by a distinct wall or membrane, 

 and w r hen mashed out is seen to consist of a skein of 

 coarse threads. Into the cytoplasm the nourishment 

 of the cell passes. Of bacteria, either in their natural 



1 See frontispiece for an example o'f cell. Nearly all living cells are 

 comparable to these leukocytes. 



