CELL MULTIPLICATION 



substance which is rich in proteins, has but slight affinity for stains, and is 

 supposed to be fluid. 



The network is composed of limn or achromatin, a transparent unstain- 

 able framework; and of chromatin, which stains deeply. It is supported by 

 the linin, and occurs sometimes in the form of granules, but usually as irreg- 

 ular anastomosing threads, both thicker primary fibers and thinner connect- 

 ing branches. The threads often form thickened nodes, karyosomes or 

 false nucleoli, at their points of intersection. It is now quite generally be- 



Cell membrane. 



Metaplasm gran- <- 

 ules. 



Karyosome or net- 

 knob. 



Hyaloplasm. 



Spongioplasm. 



Linin network. * 



Nucleoplasm. -' 



Attraction sphere. 

 Centrosome. 



Plastids. 



... Chromatin network 



- Nuclear membrane 



'* Nucleolus. 



Vacuole. 



FIG. 14. Diagram of a Typical Cell. (Bailey.) 



lieved that the chromatin occurs as short, rod-like, and highly refractive 

 masses, which are embedded in the linin in a regular series. 



The nucleoli, or plasmosomes, are spherical bodies which stain deeply, and 

 may either lie free in the nuclear matrix or be attached to the threads of 

 the network. 



The Centrosome and Attraction Sphere. In addition to the nucleus, 

 a minute spherical body called the centrosome is believed to be constantly 

 present in animal cells, though sometimes too small to be demonstrated. 

 The centrosome is smaller than the nucleus, close to which it lies, and exerts a 

 peculiar attraction for the protoplasmic filaments and granules in its vicinity, 

 so that it is surrounded by a zone of fine radiating fibrils, forming the attrac- 

 tion sphere or archoplasm. Some authorities assert that the centrosome 

 lies within the nucleus in the resting state, and passes into the cell proper only 

 in the earlier stages of cell division. The attraction sphere is most distinctly 

 seen in cells about to divide. It plays an important role in nuclear division, 

 but it is doubted if it gives the initial impulse to the process. 



Cell Multiplication. Cells increase in number by a process known 

 as cell division, of which the first act is nuclear division, In fact the nucleus 

 is the center of control of the cell mass in the process of division. Cell multi- 



