138 



THE ESSENTIALS OF HISTOLOGY 



FIG. 1G9. SECTION OF DOG'S SURMAXILLARY, STAINED. 



a, duct ; 6, alveolus ; c, crescent. 



FIG. 170. SECTION OF PART OF THE HUMAN SUUMAXILLARY GLAND. 



To the right of the figure is a group of mucous alveoli, to the left a group of serous alveoli. 



FIG. 171. ALVEOLI OF A SEROUS GLAND. A, AT REST. B, AFTER A SHORT PERIOD 



OF ACTIVITY. C, AFTER A PROLONGED PERIOD OF ACTIVITY. 



In A and B the nuclei are obscured by the granules of zymogen. 



