78 



PHYSIOLOGY 



CHAP. 



Their total area diminishes from loss of clear cytoplasm; the 

 granular substance on the contrary increases, so that the cell 

 appears more clouded, the nucleus becomes rounded with more 

 regular outlines, and the nucleolus is plainly visible (Fig. 21, B). 



Microscopic preparations of mucous glands treated in the same 

 way show in the resting state large clear cells with colourless 

 cytoplasm, which consists of a very tine filamentous network with 

 large meshes, filled with an amorphous, shining, mucinogenous 

 substance, which resembles small granules. The nucleus stains 

 with carmine ; it has no visible nucleolus, and is always situated at 



Fio. 23. Rabbit's parotid in fresh state. (Langley.) A, resting state ; B, after injection of 

 weak doses of pilocarpine ; C, after stimulation of cervical sympathetic ; D, after more 

 prolonged stimulation of this nerve. 



the periphery or margin of the cell (Fig. 22, A). After prolonged 

 secretion excited by stimulation of the secretory nerves, the cells 

 appear much reduced from loss of the clear muciuogenous 

 substance, the cytoplasm stains, the nucleus is rounded, with a 

 distinct nucleolus which has moved to the centre of the cell 

 (Fig. 22, B). 



The subject of these histological researches is (as Heidenhain 

 points out) not the living cell, but its dead body, altered, moreover, 

 by the technique of hardening and staining. Yet, since the 

 phenomena are so constant, we may safely conclude that the 

 living cells also are differently constituted in the resting and in 

 the active state, owing to the manufacture of secretion. Eecent 

 comparative researches on gland cells in fragments of living gland 

 fresh from the body, show that while their microscopic appearance 



