126 



MANUAL OF PHYSIOLOGY. 



glands, from their being made up of numerous acini, or minute 

 elongated sacs or tubules, arranged at the end of a repeatedly 

 branching duct, like grapes on the terminals of the successive 

 little branches growing from the central stalk to form a bunch. 

 In the glands the saccules are packed together closely around 

 the ducts, and by mutual pressure are made to assume various 

 shapes. The wall of the saccule is formed of a very delicate 



FIG. 



Section of the Subrnaxillary Gland of the Dog, showing the comnuMxv- 

 ment of a duct in the alveoli. X 42">. (Schiifer.) a. One of the alveoli, 

 several being grouped round the ductlet (d/). b. Basement membrane in 

 section, d. Larger duct with columnar epithelium, s. Half-moon group of 

 cells. 



clear transparent membrane, on the outside of which are numer- 

 ous flattened branching stellate cells, the branches of which 

 anastomose one with another, and appear also to penetrate the 

 membrane in order to reach the inside of the acini. 



The cavity of the little sacs is almost completely filled with 

 large polygonal gland-cells, so that only a very narrow space exists 

 in the centre. (Fig. 61.) From this space, there is free communi- 



