386 



THE DIGESTIVE SYSTEM 



tivity. During rest the granular secretion accumulates within the cell, 

 until the non-granular zone is reduced to a narrow rim at its basal 

 extremity and the nucleus is obscured and pushed somewhat basalward. 

 The cell becomes therefore much swollen and the alveolar lumen almost 

 obliterated. During activity the zymogen granules are discharged into 

 the lumen; the cell shrinks and becomes clearer; the nucleus appears 

 more distinct, and the granular zone becomes progressively narrower, 



the basal non-granular 

 zone being correspon- 

 dingly increased in 

 breadth. In this basal 

 zone elongated gran- 

 ules have been demon- 

 strated, which in part 

 are to be regarded as 

 prozymogen ('basal 

 filaments' of Solger), 

 in part (revealed by 



V yr ^ ^55** *, *# g* special technic) as 



\ ^"difc'j *^ *JiJ i *J mitochondria. 



"4* v i^feL~*fii W r ^ ne serous cells 



^j 7 lj^ 'r'^V *** are provided with sys- 



tems of secretory ca- 

 naliculi which, begin- 

 ning at the glandular 

 lumen, invest the cell 

 with a network of 

 canals which lie in the 

 intercellular substance 



and may even send short offshoots or intracellular canaliculi into the 

 body of the cell itself. These canaliculi are considered to be character- 

 istic of the serous acini and are not found in relation with the cells of 

 the mucous acini (Fig. 358). 



THE Mucous ACINI. The mucous acini may contain only mucus- 

 secreting epithelium, or they may also include certain finely granular 

 acidophil cells which resemble the epithelium of the serous glands. The 

 former variety of acinus is found in the mucous glands at the base 

 of the tongue and in the soft palate; the latter in the sublingual gland, 

 in Ihe lingual glands of Nuhn, and in the mucous glands of the lips 

 and cheeks. 



^ 



FIG. 356. A GROUP OF Mucous ACINI, FROM THE 

 HUMAN SUBMAXILLARY GLAND. 



a-a, interlobular connective tissue, 

 eosin. Photo. X 510. 



Hematein and 



