DIGESTION IN THE MOUTH 



717 



FIG. 342. Submaxillary gland of rabbit. 

 (ScHAFER after E. MULLER.) 



The cells, all serous, are in different functional 

 states : a, a loaded cell ; b, a discharged cell ; c, a 

 secretory canaliculus penetrating into a cell. 



From an examination of the stained specimens of glands the following 

 stages in the production of secretion have been described : 



(1) In the neighbourhood of the nucleus, and probably with its active 

 co-operation, a differentiation of the protoplasm occurs with the production 

 in most cases of a basophile 



substance which in hardened 

 specimens generally takes the 

 appearance of filaments. Since 

 these filaments are sometimes 

 regarded as the working part 

 of the protoplasm, they have 

 been given the name of ergas- 

 toplasm (Fig. 343, c and r). 



(2) By a modification of 

 the ergastoplasm granules are 

 formed. After their first 

 appearance these granules 

 undergo gradual modification, 

 as is shown by the fact that 

 the staining reactions of the 

 granules near the base of the 

 cell differ from those of the granules 

 at the free margin. 



(3) When the secretion is ex- 

 cited, the fully formed granules 

 take up water and salts in vary- 

 ing proportions, swell up, and 

 discharge their contents into the 

 lumen of the alveolus as the 

 secretion proper to the gland. 



ELECTRICAL CHANGES 



Every localised chemical change 

 in a system permeated by electro- 

 lytes must give rise to electrical 

 differences of potential. It is 

 therefore natural that electrical changes should accompany the intense 

 chemical activity which is associated with secretion. The 'interpretation of 

 these changes is difficult, owing to the simultaneous operation of another 

 factor which may determine electrical differences of potential, namely, 

 the movement of fluids through porous membranes. If the hilum of 

 the submaxillary gland and its outer surface be connected with a 

 galvanometer, a resting difference of potential is nearly always found, 

 generally in such a direction that the outer surface .is positive. to the 

 hilum. The current through the gland is therefore from within out. On 

 exciting the chorda tympani nerve a diphasic effect is generally obtained, 



- 343. Cells of pancreas, showing succes- 



sive stages in activity, A,B,C,D. A, resting: 

 Dj discharged gland. (MATHEWS.) 



