150 



NORMAL HISTOLOGY. 



gland does not possess a distinct capsule and consists of an aggregation of 

 separate glands, each of which has its independent duct, rather than a con- 

 solidated single organ. 



The sublingual gland belongs to the mixed mucous type and possesses 

 a curtailed duct-system, in which distinctive intralobular and intermediate 

 ducts are wanting. The interlobular ducts subdivide into smaller canals that 

 enter the primary lobules and give off wider passages lined with cuboidal 

 epithelium. Towards the distal ends of these terminal canals the mucous 

 gland-cells appear, at first isolated or in groups, until they constitute the 

 entire lining of the passage. The condition of the alveoli, as regards the 

 mucus-producing cells, varies even in the same lobule. Sometimes an entire 

 primary lobule is composed of alveoli filled with mucous cells; at other times 



Duct 



Demilunes of 

 serous cells 



FIG. 190. Section of sublingual gland, showing serous cells grouped as demilunes. X 270. 



empty and engorged alveoli alternate, or the depleted acini may predominate. 

 The demilunes of serous cells are also uncertain, since these may be absent or 

 present in considerable numbers and of large size. The relatively wide lumen 

 of the alveoli and the more pronounced reticulated appearance of the gland- 

 cells distinguish the exhausted sublingual gland from the parotid under like 

 conditions. 



The normal secretions of the salivary and oral glands contain no formed 

 elements, although granules and cellular remains may be present. The 

 spherical so-called salivary corpuscles, which occur in varying numbers in 

 the mixed oral secretion, have no relation to the salivary glands, 'since they 

 are only modified lymphocytes which have escaped from the lymphoid tissue 

 of the faucial and lingual tonsils. On entering the mouth, these cells are 

 affected by the saliva and become greatly swollen, the granular remains of 

 their cytoplasm exhibiting molecular motion to a marked degree. 



The blood-vessels of the salivary and larger oral glands follow the 

 same general arrangement. The larger arteries accompany the ducts in 

 their course within the interlobular connective tissue, giving off twigs which 

 supply the walls of the excretory passages. From the interlobular vessels, 



