PHYSIOLOGY OF THE CELL. 



2 7 



The nucleus is a small vesicular body embedded in the cytoplasm near 

 the center of the cell. In the resting condition of the cell it consists of a 

 distinct membrane, composed of amphipyrenin, inclosing the nuclear contents. 

 The latter consists of a homogenous amorphous substance the nuclear 

 matrix in which is embedded the nuclear network. It can often be seen 

 that a portion of one side of the nucleus, called the pole, is free from this net- 

 work. The main cords of the network are arranged as V-shaped loops about 

 it. These main cords send out secondary branches or twigs, which, uniting 



Nuclear mem- 

 brane. 



Linin. v 



Nuclear fluid 



Nucleolus. . . 



Chromatin cords 

 (nuclear network). 



Nodal enlargement 

 of the chromatin. 



_ . Cell membrane. 



Exoplasm. 



-, Microsomes. 

 Centrosome. 



Spongioplasm. 

 Hyaloplasm. 



- Foreign inclo- 

 sures. 



FIG. 2. DIAGRAM OP A CELL. 

 Microsomes and Spongioplasm are only partly drawn. 



with one another, complete the network. The nuclear cords are composed 

 of granules of chromatin so called because of its affinity for certain staining 

 materials held together by an achromatin substance known as linen. Besides 

 the nuclear network, there are embedded in the nuclear matrix one or more 

 small bodies composed of pyrenin known as nucleoli. At the pole of the nu- 

 cleus, either within or just without in the cytoplasm, is a small body, the cen- 

 trosome, or pole corpuscle. 



Chemic Composition of the Cell. The composition of living pro- 

 toplasm is difficult of determination, for the reason that all chemic and phys- 

 ical methods employed for its analysis destroy its vitality, and the products 

 obtained are peculiar to dead rather than to living matter. Moreover, 



