218 



Tin: ORGANS 



believe that in most cases the cell is reconstructed from the nucleus 

 and unchanged cytoplasm, and again passes through the process of 

 secretion. In stratified epithelium secretion may begin while the cell 

 is still deeply situated, but is completed only as the cell reaches the 

 surface, where its mucus is to be discharged. 



In describing the vital properties of cells (p. 50) attention was called to the 

 fact that all cells take up from the surrounding blood and lymph substances 

 required for their own nutrition, and give off waste products (excretions). In 

 such sense all cells secrete and excrete. What distinguishes the gland cell is 

 that in addition to carrying on its own metabolism (p. 51) it manufactures a 



specific substance not for its own use 



^- 





<?/-, 



7 



Fig. 131. — Gland Cell from Pancreas of 

 Salamander; n, Nucleus; cs, caryosomes; 

 pi, plasmosomes; cp, paranucleus; erg, 

 ergastoplasm filaments; g, secretory gran- 

 ules. X500. (Prenant.) 



but to be extruded from the cell, and 

 used elsewhere in the body (secretion, 

 e.g., gastric juice), or discarded (excre- 

 tion, e.g., urine). Such a cell takes up 

 from blood or lymph the substances 

 required, more or less completely as- 

 similates them, and finally transforms 

 ihem into its specific secretion. 



Certain changes, other than those 

 described as seen in the mucous secret- 

 ing cell, may occur in the protoplasm 

 of actively secreting gland cells. In 

 many cells there appears at the onset of 

 secretion a modification of the cytoplasm 

 which has been designated ergastoplasm^ 

 (Fig. 131). In some cells the ergasto- 

 plasm takes the form of slender threads 

 near the base of the cell, basal filaments, 

 in others of minute rods. Other forms have been described as mitochondria, 

 cytosomes, pseudochromosomes, etc. 



Many gland cells have intracellular secretory canals (see p. 47). 

 In some gland cells a body known as the paranucleus appears at the beginning 

 of secretion. It is a rather large, usually irregular mass, differing in staining 

 qualities from the nucleus and probably being of the same nature as, or closely 

 allied to the ergastoplasm. Its relation to either of these structures, to the 

 cytoplasm, or to the secretion is not known. 



The function of the nucleus in secretion is apparently of great importance. 



'A multiplicity of terms has arisen (ergastoplasm, basal filaments, kinoplasm, 

 paraneucleus, protoplasma superieur, etc.) to designate substances which appear under 

 varj'ing conditions in many types of cells. These substances dilTcr in appearance in 

 different cells, which accounts for the various terms applied to them. The}- differ 

 from the ordinary protoplasm of the cell both in appearance and in their reactions 

 to stains. They are most in evidence when the activities of the cells are at their 

 maximum. They "are all specializations of the cytoplasm; products elaborated within 

 the cell in the performance of its special functions. 



