II 



EXTERNAL DIGESTIVE SECRETIONS 



69 



the gland is termed mucous ; when the alveolar walls are constructed 

 partly of mucous, partly of albuminous cells (e.g. the submaxillary 

 and suborbital of many mammals, part of the submaxillary in 

 man, and the majority of the scattered buccal glands), the gland, 

 as a whole, is termed mixed. In this case the albuminous glands 

 occupy a marginal position, and usually form little crescentic 

 masses known as the demilunes or crescents of Giannuzzi (Fig. 19). 

 The epithelial cells which line the intercalary and interlobular 

 excretory ducts are quite different from the secreting cells. The 

 ductules of lesser and medium calibre are lined with flattened, 

 cubical, striated cells ; the larger ducts with columnar, epithelial 



Fie. "20. A, section of alveoli from human subliiigual gland. Silver eliminate method. (E. 

 Miiller.) I, lumen of intra-alveolar excretory ducts, stained black, and terminating in diverti- 

 eula which penetrate into the cells of the alveoli ; h diverticula penetrating into crescent cells. 

 B, section of alveolus from dog's submaxillary gland. Silver chromate method. (G. Retzius.) 

 Shows diverticula of excretory ducts extending into crescents of Giannu//i. Also vry tine 

 varicuse nerve fibrils which form a network with large meshes between the alveolar cells. 



cells. If the ducts are injected before making a microscopical 

 preparation, or treated with Golgi's method, which stains the 

 entire system of excretory channels a uniform black, the lumen 

 can be followed into the alveoli, and is seen to end in terminal 

 diverticuli, which penetrate between the cells, and enter for a 

 short distance into the protoplasm (Fig. 20, A, B). 



Both the serous and the mucous salivary glands are supplied 

 by two kinds of nerves, those of cranial and those of sympathetic 

 origin. The former, for the submaxillary and sublingual glands, 

 originate in the roots of the facial nerve as the chorda tympani, 

 unite with the lingual branch of the fifth nerve, and then run 

 through the submaxillary ganglion to the parenchyma of the 

 gland. For the parotid, the cranial fibres from the glosso- 

 pharyngeal nerve run through Jacobsou's nerve, the small super- 



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