Digestion. 109 



tions, the cells are found filled with granules much larger 

 than those of a serous gland, and a nucleus is seen occu- 

 pying one edge of the cell (Fig. (i, a . During activity the 

 granules are passed into the lumen of the gland, but they 

 do not leave behind them in the cells the same clear space 

 seen in the serous cell (Fig. 6, b). If the cells while in 

 an active condition be acted upon by water or dilute acetic 

 acid, they swell up and become transparent owing to the 

 mucin they contain, and a delicate network is seen to 

 invade the cell (Fig. 6, a'). A similar appearance is pro- 

 duced in the exhausted cell (Fig. 6, b'), excepting that less 

 transparent mucin is seen and more granular substance, 

 whilst the nucleus of the exhausted irrigated gland is seen 

 passing towards the centre of the cell instead of remaining 

 towards the outer wall. 



In hardened specimens of mucous glands, towards the 

 outer edge in some of the acini, cells may be found shaped 

 like half- moons or crescents, but are not loaded with mucin, 

 since they stain with carmine which stains mucin with 

 difficulty. These crescents of Gianuzzi are not found in 

 hardened preparations of serous glands. 



The outcome of these changes proves that the organic 

 elements found in the salivar} r secretion are manufactured 

 by the cells in the glands, whilst the inorganic constituents 

 are probably the result of the transudation through the 

 cells, of the lymph which reaches them through the lymph 

 passages, though experiments made by Langley and Fletcher* 

 go to prove that even water and salts are the result of an 

 act of cell secretion and not of mere transudation. 



Stomach Digestion. 

 The subject of stomach digestion in the horse has been 

 worked out only by means of feeding experiments, as it has 

 been found impossible to establish a gastric fistula in this 

 animal owing to the distance the stomach lies from the 

 abdominal wall; pure gastric juice has, therefore, probably 

 never been obtained from the horse. 



* Phil. Trans., 1889, vol. clxxx., B., p. 10'.'. Quoted by Halliburton. 



