SECRETION PHYSIOLOGY. 329 



in the nucleus becoming round and moving toward the center 

 of the cell. These changes are identical in kind with, though 

 taking place generally more slowly than, those following stimu- 

 lation of the dilator nerve or the injection of pilocarpine. Do 

 they indicate the direct action of the nerve on the cell ? Al- 

 though they might be so interpreted, they may be readily under- 

 stood without any such assumption, as follows : Stimulation of 

 the nerve causes a compression of the cells and thus expels from 

 them their stored-up metabolic products and liquid. By this 

 means the cells discharge their products. On ceasing stimula- 

 tion the alveoli and ducts relax, and the cells take up water and 

 food from the lymph. The latter process is hastened probably 

 by a temporary vaso- dilation ensuing when the sympathetic 

 stimulation is broken. In virtue of the food, oxygen and lymph 

 thus brought to them the cells form new undifferentiated proto- 

 plasm. On several successive stimulations the accumulated 

 metabolic products are largely discharged, the cells become 

 smaller and the nuclei, relieved from pressure, become round 

 and move toward the center of the cells. The same explanation 

 holds also for the changes following stimulation of the dilator 

 secretory nerve, with the exception that the stored products are 

 dissolved out of the cell, instead of being squeezed out, and as 

 vaso-dilation accompanies this secretion the changes take place 

 at a more rapid rate. These changes are discussed more at 

 length in my paper on the Pancreas Cell.* 



i. Summary and Conxlusiox. 



The phenomena of sympathetic secretion, which have been con- 

 sidered, could hardly indicate more clearly, I think, the muscular 

 mechanism of that secretion. The sudden gush of saliva; its 

 sudden cessation, however prolonged the stimulation ; the dim- 

 inution in the amount of saliva secreted when the stimulations 

 are rapidly repeated ; the apparent paralysis of the nerve when 

 the ducts are empty and its restoral to power if the ducts be 

 passively redistended ; the augmentation in volume of the secre- 

 tion, when the ducts are abnormally full of fluid saliva, and the 



* Shortly to appear in the Journal of Morphology. 



