THE DIGESTIVE SYSTEM 



285 



are connected with the lumen ])y intercellular secretory canals (page 

 47). The interstitial tissue of the submaxillary contains numerous 

 elastic fibres. 





g f e d 



Fig. 186. — Section of Human Submaxillary Gland. X252. (Stohr.) a, IMucous 

 tubule; b, serous tubule; c, intermediate yibule; d, "secretory" tubule; e, demilune;/, 

 lumen; g, interstitial connective tissue. 



Blood-vessels. — The larger arteries run in the connective-tissue 

 septa with the ducts, giving off branches which accompany the divi- 

 sions of the ducts to the lobules, where they break up into capillary 

 networks among the tubules. These give rise to veins which accom- 

 pany the arteries. 



The lymphatics begin as minute capillaries in the connective 

 tissue separating the terminal tubules. These empty into larger 

 lymph vessels which accompany the arteries in the septa. 



The nerves of the salivary glands are derived from both cerebro- 

 spinal and sympathetic systems, and consist of both medullated and 

 non-medullated fibres. The medullated fibres are afferent, probably 

 the dendrites of cells located in the geniculate ganglion. Small 

 bundles of these fibres accompany the ducts. Single fibres leave the 

 bundles, lose their medullary sheaths, and form a non-medullated 

 subepithelial plexus, from which delicate fibrils pass to end freely 

 _among_the epithelial cells. Efferent impulses reach the gland through 

 the sympathetic. The fibres are axones of cells situated in small 

 peripheral ganglia; the cells sending axones to the submaxillary 



