THE FUNDAMENTAL PHYSIOLOGICAL ACTIONS. 19 



Indirect, Karyokinetic or Mitotic Cell Division. Before 

 attempting to describe the phenomena of indirect cell divi- 

 sions it is necessary to give some 

 account of the structure of a typical 

 primitive cell as made out in speci- 

 mens carefully prepared and studied 

 with the highest powers of the 

 microscope. The main bulk of the 

 cell, surrounding the nucleus, is the 

 cell-body, and in some cases is en- 

 closed in an envelope or sac, which, 

 however, when present, plays but a 

 secondary or passive part in cell divi- ium; e, nucleus." aaudt. together 



__, r ,. . form the cell-body. 



sion. The cell-body, known also as 



the cell-protoplasm (Fig. 7), consists of a network of extremely 

 fine threads,"the reticulum or spongioplasm, the meshes of which 

 are occupied by a different substance, the hyaloplasm : the 

 proportions of hyaloplasm and spongioplasm vary in different 

 cells and often in different parts of the same cell; in fact a 

 layer of hyaloplasm unmixed with spongioplasm frequently 

 exists on the exterior of the cell, and the hyaloplasm appears 

 to be the more immediately concerned in the activities of the 

 living cell. In addition there is to be found, imbedded in the 

 cell-body and near the nucleus or attached to it, an extremely 

 minute particle, the attraction-particle or cent r.o some, near 



which a radial arrangement of the 

 cell-substance may often be ob- 

 served. 



The nucleus (Fig. 8) of a 

 resting cell, that is of a cell not 

 in process of division, consists of 

 an amorphous material (nucleo- 

 plasm] which is perhaps similar 

 in composition to the hyaloplasm, 

 and a filamentous material, dif- 

 ferent from spongioplasm, and 

 named chromoplnsm or karyo- 



SS^pl^r^f'SrS?"^ ?* ^ P*1 ^ "S behavior 



h staining fluids and other 

 reagents karyoplasm is quite different chemically from the 

 spongioplasm of the cell-body. One or more granules (nit- 

 cleoli) which may be found within most nuclei are probably 



FIG. 8. Diagram of a resting 

 nucleus, a, nuclear membrane; fo, 

 nucleoplasm; c, nucleolus; d, chro- 

 ome of the surround- 

 m of the cell, the 

 structure of which is not indicated. 



