62 



MINUTE STRUCTURE OF CELLS 



complicated changes in the nucleus to which we must now 

 direct our attention. First of all, however, it will be neces- 

 sary to describe the exact microscopic structure of cells and 

 their nuclei as far as it is known at present. 



There seems to be a good deal of variation in the precise 

 structure of various animal cells, but the more recent re- 

 searches show that the cell-protoplasm (Fig. 9, cell-plsm) 



nucl. 

 mem b. 



nucl.plsm 



chrom. 



FIG. 9. A typical animal cell, showing cell-membrane (cell-memb.), 

 cell-protoplasm (cell-plsni), nuclear membrane (micl-meinb.}, nuclear 

 protoplasm or achromatin (uncl-phm], and coil of chromatin (chrom}. 

 (After Carnoy. ) 



consists of a finely granular substance traversed by an 

 extremely delicate network, the constituent threads of which 

 are of almost inconceivable fineness, and bounded externally 

 by a membrane (cell-memb.) of excessive tenuity. As the 

 granules of the protoplasm are to be looked upon as pro- 

 ducts of metabolism (anastates and katastates, p. 18) it is 



