10 THE ANIMAL CELL [CH. II. 



monatomic alcohol ; and inorganic salts, especially phosphates and 

 chlorides of calcium, sodium, and potassium. 



The large quantity of water present should be particularly noted ; 

 the student when first shown diagrams of the reticulum in proto- 

 plasm is apt to imagine that it consists of a firm solid, like a system 

 of wires pervading a jelly. The reticulum is only slightly more solid 

 than the hyaloplasm. 



The Nucleus. 



In form the nucleus is generally round or oval, but it may have 

 in some cases an irregular shape, and in other cases th3re may be 

 more than one nucleus in a cell. 



The nucleus exercises a controlling influence over the nutrition 

 and subdivision of the cell ; any portion of a cell cut off from the 

 nucleus undergoes degenerative changes. 



A nucleus consists of four parts 



1. The nuclear membrane, which encloses it. 



2. A network of fibres in appearance like the spongioplasm of the 



protoplasm but on a larger scale ; that is to say, the threads 

 of which it is composed are much coarser, and much more 

 readily seen. The name chromoplasm has been given to 

 this network. 



3. The nuclear sap or matrix, a more fluid and homogeneous 



substance which occupies the interstices of the spongework 

 of chromoplasm. 



4. Nucleoli ; these are of two principal varieties ; some are knots 



or thickened portions of the network (pseudo-nucleoli), and 

 others, the true nucleoli, float freely in the nuclear sap. 

 These four parts of the nucleus are represented in the next 

 diagram. 



Node of network- _ _. ^ 



*~ Nuclear membrane. 



j Nucleolus. 



Node of network ^^-^f^TT^?-"--- Nuclear matrix. 



7 

 ' Nuclear network. 



FIG. 7. The resting nucleus diagrammatic. (Waldeyer.) 



The next figure (fig. 8) gives a view of the nucleus, according to 

 the researches of Eabl. He considers that the fibres of the network 

 may be divided into thick fibres which he terms primary, and thinner 

 connecting branches which he terms secondary (shown only on the 



