I5 o TEXT-BOOK OF PHYSIOLOGY 



Histologic Changes in the Salivary Glands during Secretion. 



During and after secretion very remarkable changes take place in the cells 

 lining the acini, which are in some way connected with the production of the 

 essential constituents of the salivary fluids. In the case of the parotid gland, 

 which may be regarded as the type of a serous or albuminous gland, the 

 following changes have been observed by Langley (Fig. 64). During the 

 period of rest and just previous to secretor activity, the epithelial cells are 

 enlarged and swollen, and encroach on the lumen of the acinus. The 

 protoplasm of the cells is so completely filled with dark fine granules as not 

 only to obscure the nucleus, but almost to obliterate the line of union of the 

 cells. As soon as secretion becomes active, however, the granules begin to 

 disappear from the outer region of the cell and move toward the inner border 

 and into the lumen of the acinus. From these observations it might be 



FIG. 64. PAROTID GLAND AFTER PRO- 

 LONGED ACTIVITY. 1,1, Acini; 2, duct; 3,3, 

 albuminous cells almost free of granules; 4, 

 nuclei clear and well denned. (Semi-diagram- 

 matic.) 



FIG. 65. SUBMAXILLARY GLAND AFTER 



PROLONGED ACTIVITY. 1,1, Acini; 2, duct; 

 3,3, mucous cells free of mucin and filled 

 with fine granules; 4,4, nuclei rounded and 

 returned to the center of the cell; 5,5, cells of 

 Giannuzzi, large and distinct. (After 

 Vialleton.) 



inferred that during rest the protoplasm of the cells gives rise to granular 

 material, and that during and after secretor activity there is an absorption 

 of new material from the lymph and a reconstruction of the granular material. 



In the submaxillary gland, a portion of which may be taken as a type of a 

 mucous gland, similar changes have been observed (Fig. 65). During rest 

 the epithelial cells are large, clear in appearance, highly refractive, and loaded 

 with small globules resembling mucin. The nucleus, surrounded by a small 

 quantity of protoplasm, lies near the margin of the cell. That the granules 

 are not protoplasmic in character is shown by the fact that they do not stain 

 on the addition of carmine. When treated with water or dilute acids, the 

 globules swell, coalesce, and form a uniform mass. The chemic relations 

 of this substance indicate that it is the precursor of mucin namely, mucigen. 

 During secretor activity the cells discharge these mucigen granules into the 

 lumen of the acinus where they are transformed into mucin. Though the 

 appearance of the gland-cell indicates it, there is no evidence for the view 

 that the cell itself undergoes disintegration in the process. 



The Physiologic Actions of Saliva. The constant presence of salivary 

 glands in the different classes of animals and the large amount of secretion 

 they pour daily into the alimentary canal point to the conclusion that this 

 mixed fluid plays an important r61e in the general digestive process. Experi- 



