38 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



able elasticity. Independent movement of the nu- 

 cleus in the cytoplasm has often been observed. At 

 the same time its relation to the cytoplasm is a most 

 intimate one and many cytoplasmic particles doubt- 

 less have their origin in the nucleus. 



The structure of the nuclear protoplasm is even 

 more complex than that of the cytoplasm. A reticu- 

 lum of coarse, thread-like texture is constantly 

 present. This stains deeply and is therefore called 

 chromatin. The chromatin threads, like the spongio- 

 plasm of the cytoplasm, are made up of minute 

 particles or granules compactly arranged in rows 

 that cross and interlace, making nodal points here 

 and there called nuclear net-knots. The chromatin 

 is imbedded in or deposited on a less stainable reticu- 

 lum called linin, and surrounding both chromatin 

 and linin everywhere, and filling their meshes, is a 

 semifluid substance that does not readily stain and is 

 therefore called achromatin, nuclear sap, paralinin, 

 or karyolymph. 



Imbedded in the achromatic substance are one 

 or more spherical bodies called nucleoli. The nucleoli 

 stain less heavily than the chromatin and may be 

 dissolved by reagents that do not affect the chro- 

 matin; therefore, they are composed of a substance 

 not identical with the latter. Their function is not 

 known. The nucleus is usually enclosed in a thin 

 nuclear membrane (amphipyrenin) not unlike chro- 

 matin material. This membrane has perforations 

 which allow a free communication between the achro- 

 matic fluid of the nucleus and the cytolymph and 



