258 



THE SALIVARY GLANDS. 



lymph-cavities, and beyond these the blood-capillaries run in a net-like 

 meshwork. The lymph- vessels leave the gland at the hilum. 



The secreting cells are of varying structure, accordingly as the sali- 

 vary gland secretes mucus (sublingual gland in man, submaxillary gland 

 in the dog) or albumin (parotid gland in man), or is a mixed gland 

 (submaxillary gland in human beings). 



Two kinds of cellular elements are found in the acini of the sub- 

 maxillary gland of the dog and the sublingual gland of human beings: 

 (i) The so-called mucous cells (Fig. 94, B, c), which bound the secretory 

 cavity. They possess a membrane and are filled with a flattened 

 nucleus turned toward the acinus- wall. Centrosomes are difficult to 

 recognize. The cell-body is abundantly impregnated with mucin, which 



gives it a bright, highly refractive ap- 

 pearance. On account of their mucous 

 contents the cell-bodies hardly stain 

 with carmine at all, while the nucleus 

 takes up the stain. A process given off 

 by the cell applies itself in a curved 

 manner to the inner wall of the acinus. 

 The true protoplasm of the cell is 

 drawn out in a thread-like network 

 from the nucleus through the mucin- 

 mass. (2) The other variety of cellular 

 elements form crescent-shaped complex 

 bodies (Fig. 94, B, d) Gianuzzi's cres- 

 cents, Heidenhain's composite marginal 

 cells that lie in direct contact with the 

 wall of the acinus. Each crescent con- 

 sists of a number of small, closely 

 packed, angular cells, with albuminous 

 contents and nuclei and separated with 

 difficulty. They are granular, darker, 

 without mucous contents, easily impreg- 

 nated by stains, and exhibit secreting 

 spaces between the cells. 



The parotid gland (Fig. 95), secret- 

 ing albumin in man and in mammals, 

 contains but one kind of secretory cells, 

 namely, cubical cells, with a coarse-meshed protoplasm, staining little 

 with pigments, without a membrane, with serrated, readily stained, 

 centrally situated, highly refractive nuclei, without nucleoli, with secre- 

 tory ducts between them. The smaller cells of the salivary tubules 

 bear a diplosoma near their free surface. The salivary glands of 

 animals that secrete saliva free from mucus present similar features. 



By means of fine ducts, the so-called intercalary pieces, the terminal portions 

 of the glands communicate with the thicker salivary tubules. The cells of these 

 tubules, which, in their outer portions, appear fibrillated, and at times contain 

 yellow granules (Fig. 94, E), bear a diplosoma near the surface. These salivary 

 tubules empty into the excretory ducts. It is not improbable that these different 

 portions of the gland also secrete different constituents of the saliva. 



FIG. 95. Diagrammatic Representation of a 

 Salivary Gland: a, excretory duct; r, r, 

 salivary tubules; s, intercalary portion; 

 e, e, terminal portions. P, terminal por- 

 tions of the parotid gland, with intercel- 

 lular secretory ducts (stained black), 

 passing over into the excretory duct (a) 

 of the intercalary portion (s); r, parotid 

 cell at rest; t, the same cell after secre- 

 tion. 



