THE SALIVARY GLANDS. 



695 



in consequence of prolonged activity, and these changes may be 

 recognized both in preparations from the fresh gland and in preserved 

 specimens. In the parotid gland Heidenhain studied the changes in 

 stained sections after hardening in alcohol. In the resting gland 

 the cells are compactly filled with granules that stain readily and are 

 imbedded in a clear ground substance that does not stain. The 

 nucleus is small and more or less irregular in outline. After stimula- 

 tion of the tympanic nerve the cells show but little alteration, but 

 stimulation of the sympathetic produces a marked change. The 

 cells become smaller, the nuclei more rounded, and the granules 

 more closely packed. This last appearance seems, however, to be 



Fig. 266. Parotid gland of the rabbit in a fresh state, showing portions of the secret- 

 ing tubules: A, In a resting condition; B, after secretion caused by pilocarpia; C, after 

 stronger secretion, pilocarpm and stimulation of sympathetic; D, after long-continued 

 stimulation of sympathetic. (After Lcmgley.') 



due to the hardening reagents used. A truer picture of what occurs 

 may be obtained from a study of sections of the fresh gland. Lang- 

 ley,* who first used this method, describes his results as follows: 

 When the animal is in a fasting condition the cells have a granular 

 appearance throughout their substance, the outlines of the different 

 cells being faintly marked by light lines (Fig. 266, A}. When the 

 gland is made to secrete by giving the animal food, by injecting 

 pilocarpin, or by stimulating the sympathetic nerves, the granules 

 begin to disappear from the outer borders of the cells (Fig. 266, B) fi 

 so that each cell now shows an outer, clear border and an inner, 

 granular one. If the stimulation is continued the granules become 



* "Journal of Physiology," 2, 260, 1879. 



