282 



THE STRUCTURE OF THE SALIVARY GLANDS. 



alveoli in addition to this basket-shaped structure. Immediately out- 

 side this membrane is a lymph-space (Gianuzzi), and outside this again 

 the net-work of capillaries is distributed. [The extent to which this 

 lymph-space is filled with lymph determines the distance of the capil- 

 laries from the membrana propria. The interalveolar lymph-spaces 

 communicate with large lymph-spaces between the lobules, which in 

 turn communicate with perivascular lymphatics around the arteries 

 and veins.] The lymphatics emerge from the gland at the hilum. 



The secretory cells vary in structure, according as the salivary gland 

 is a mucous [sub-maxillary and sub-lingual of the dog and cat], a 

 serous [parotid of man, and mammals, and sub-maxillary of rabbit], 

 or a mixed gland [human sub-maxillary and sub-lingual]. 



Mucous Acini. The secretory cells of mucous glands, and the 

 mucous acini of mixed glands (Fig. 117), are lined by a single 

 layer of " mucin cells " (Heidenhain) (Fig. 116, B, c), which are large 

 cells distended with mucin, or at least with a hypothetical sub- 

 stance, mucigen, which yields mucin. The mucin cells are more 

 or less spheroidal in shape, clear, shining, highly refractive, and 

 nearly fill the acinus. The flattened nucleus is near the wall of the 



acinus. Each cell has a 

 fine process which over- 

 laps the fixed part of the 

 cell next to it. Owing 

 to the fact that the body 

 of each cell is infiltrated 

 with mucin, these cells do 

 not stain with carmine, 

 although the nucleus and 

 its immediately investing 

 protoplasm do. Another 

 kind of cell occurs in the 

 sub-maxillary gland of the 

 dog. It forms a half- 

 moon-shaped structure 

 (Gianuzzi) lying in direct 

 contact with the wall of 

 the acinus. Each " half- 

 moon " or " crescent " con- 

 sists of a number of small, 

 closely packed, angular, 

 strongly albuminous cells with small oval nuclei, which, however, are 

 separated only with difficulty. Hence, Heidenhain has called them 

 " composite marginal cells " (B, d.} They are granular, darker, devoid 



Fig. 117. 



Section of part of the human sub-maxillary 

 gland. On the left of the figure is a group 

 of serous alveoli, and on the right a group 

 of mucous alveoli. 



