240 



ELEMENTARY PHYSIOLOGY 



cell stains readily (Fig. 73, B). In the parotid gland the 

 cells are simihirhj smaller, the nucleus more distinct, 

 and the cell-substance stains more readily than in the 

 condition of rest (Fig. 74, B). 



If instead of taking sections of the hardened gland a 

 piece of the fresh parotid be examined in the two states of 

 rest and activity the differences shown in Fig. 75 may be 

 seen. 



At rest the cells are full of granules throughout, as in 

 Fig. 75, A. After activity the granules are fewer and 

 now lie near the inner end of the cells as in G. Between 



Fig. 75.— Changes in the PARorin Gland during Secreting 

 Activity. (Slightly ihaorammatic.) 



these two extremes there is an intermediate stage shown 

 inB. 

 6. The Nervous Control and Nature of Salivary 



Secretion. — We have described in ihv iireceding section 

 the differences which may be observed Vjetween the cells 

 of a resting gland and of the same gland after it has been 

 secreting. Let us now see what may be learnt from a 

 study of these differences and of the way in which they 

 may be brought about. 



In the first place the differences in the size and appearance 

 of the cells in the two conditions seem to show quite 

 clearly that while at rest they build up material which is 

 stored in their substance and hence the cells are large. 



