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HANDBOOK OF PHYSIOLOGY. 



tween the basement membrane and the central cells. The cells compos- 

 ing the mass are small, and have a very dense reticuluin, the nuclei are 

 spherical, and increase in size during secretion. In the mucous gland 

 there are some large tubes, lined with large transparent central cells, and 

 having besides a few granular parietal cells ; other small tubes are lined 

 with small granular parietal cells alone ; and a third variety are lined 

 equally with each kind of cell. 



(3) In the muco-salivary or mixed glands, as the human submaxillary 



Fig. 236. 



Fig. 237. 



Fig. 236. Section of the submaxillary gland of a dog, during rest Most of the alveolar cells 

 are large and clear, being filled with the material for secretion (in this case, mucigen) which 

 obscures their protoplasm: some of the cells, however, are small and protoplasmic, forming the 

 crescents seen in most of the alveoli. (Ranvier. ) 



Fig. 237. Section of a similar gland after a period of activity. The mucigen has been dis- 

 charged from the mucin-secreting cells, which consequently appear shrunken and less clear. 

 Both the cells and the alveoli are much smaller, and the protoplasm of the cells is more apparent. 

 The crescents of Gianuzzi are enlarged. (Ranvier.) 



c, Crescent cells; gr, mucus-secreting cells; Z, lumen of alveolus. 



gland, part of the gland presents the structure of the mucous gland, 

 while the remainder has that of the salivary glands proper. 



Nerves and Blood-vessels. Nerves of large size are found in the sali- 

 vary glands ; they are principally contained in the connective tissue of 

 the alveoli, and in certain glands, especially in the dog, are provided 

 with ganglia. Some nerves have special endings in Pacinian corpuscles, 

 some supply the blood-vessels, and others penetrate the basement mem- 

 brane of the alveoli and end upon, but not in, the salivary cells. 



The blood-vessels form a dense capillary network around the ducts of 

 the alveoli, being carried in by the fibrous trabeculae between the alveoli, 

 in which also begin the lymphatics by lacunar spaces. 



The so-called mucous glands of the mouth and tongue present in some 

 cases the structures of mucous, in others of serous glands. 



