HISTOLOGICAL CHANGES IN THE SALIVARY GLANDS. 283 



of mucin, and stain readily with pigments. [In the sub- maxillary 

 gland of the cat there is a complete layer of these " marginal " 

 carmine-staining cells lying between the mucous cells and the mem- 

 brana propria.] 



[Serous Acini. In true serous glands (parotid of man and mammals) 

 and in the serous acini of mixed glands, the acini are lined by a single 

 layer of secretory columnar finely granular cells, which in the quiescent 

 condition completely fill the acinus, so that scarcely any lumen is left. 

 Just before secretion, or when these cells are quiescent, Langley has 

 shown that they are large and filled with numerous granules, which 

 obscure the presence of the nucleus. As secretion takes place, these 

 granules seem to be used up or discharged into the lumen; at least, the 

 outer part of each cell gradually becomes clear and more transparent, 

 and this condition spreads towards the inner part of the cell.] 



[In the mixed or muco-salivary glands (Klein), (e.g., human sub- 

 maxillary), some of the alveoli are mucous and others serous in their 

 characters, but the latter are always far more numerous, and the one 

 kind of acinus is directly continuous with the others (Fig. 117)]. 



143. Histological Changes during the Activity of 



the Salivary Glands. 



[The condition of physiological activity of the gland-cells is accom- 

 panied by changes in the histological characters of the secretory cells.] 



[Serous Glands. The changes in the secretory cells have been care- 

 fully studied in the parotid of the rabbit. The histological appearances 

 vary somewhat, according as the glands are examined in the fresh 

 condition or after hardening in various reagents, such as absolute 

 alcohol. When the gland is at rest, in a preparation hardened in 

 alcohol, and stained with carmine, the cells consist of a pale, almost 

 uncoloured substance, with a few fine granules, and a small irregular 

 red-stained, shrivelled nucleus, devoid of a nucleolus. The appearance 

 of the nucleus suggests the idea of its being shrivelled by the action of 

 the hardening reagent (Fig. 1 1 8)]. 



[During activity, if the gland be caused to secrete by stimulating 

 the sympathetic, all parts of the cells undergo a change (Figs. 118, 119) 

 (1) The cells diminish somewhat in size; (2) the nuclei are no longer 

 irregular, but round, with a sharp contour and nucleoli ; (3) the sub- 

 stance of the cell itself is turbid, owing to the diminution of the clear 

 substance, and the increase of the granules, especially near the nuclei ; 

 (4) at the same time, the whole cell stains more deeply with carmine 

 (Heidenhain). 



