HANDBOOK OF PHYSIOLOGY. 



Their position in the cell is very variable. In many cells, especially 

 where active growth is progressing, two or more nuclei are present. 



Structure of Nuclei. 



The nucleus when in a condition of rest is bounded by a distinct 

 membrane, the nuclear membrane, possibly derived from the spoagio- 

 plasm of the cell, which encloses the nuclear contents or Tcaryoplasm. 

 The membrane consists of an inner, or chromatic, and an of outer, or 



Node of meshwork 



Node of ineshwork LTrr 



-Ii~ Nuclear membrane. 

 ... Nncleolns. 



Nuclear matrix. 



Nuclear meshwork. 



Fig. 10. The resting nucleus diagrammatic. (Waldeyer.) 



achromatic layer, so called from their reaction to stains. The karyo- 

 plasm is made up of a reticular network, or cliromoplasm, whose in- 

 terspaces are filled by the karyolymph, or nil clear malrix^ a homogeneous 

 substance which is rich in proteids, has but slight affiuity for stains, 

 and is supposed to be fluid. 



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

 unstainable framework; and of chromatin, which stains deeply, is sup- 



Fig. 11. Diagram of nucleus showing the arrangement of chief chromatic filaments. A. Viewed 

 from the side, the polar end being uppermost, p.c.f., Primary chromatic filaments; n., nucleolus; 

 n.o.m., node of meshwork. B. Viewed at the polar end. l.c.f.. Looped chromatic filament; './., ir- 

 regular filament. (Rabl.) 



ported by the linin, and occurs sometimes in the form of granules, but 

 usually as irregular anastomosing threads, both thicker primary fibres 

 and thinner connecting branches. The threads often form thickened 

 nodes, karyosemes or false nucleoli, at their points of intersection. It 



