



CHAPTEK VII. 

 Glands. 



Definition. GLANDS are organs which present a great variety 

 in their size and shape ; they consist essentially of 

 enclosed cavities, lined or filled with cells, and open- 

 ing upon the surface of the skin, or of a mucous 

 membrane, either directly, or by means of special 

 canals known as their excretory ducts. 



Certain organs composed of one or more cavities, 

 closed on all sides, and filled by cells or globules, are 

 called blood-glands, and duct-less follicles. 



The parenchyma of glands (the essential or secret- 

 ing portion of the organ) is made up either of tubes, 

 or of partially closed vesicles, grouped together in 

 parcels, like clusters of fruit, and opening into a 

 common canal or outlet. Hence we speak of two 

 sorts of glands : those composed of clusters of vesi- 

 cles (racemose), and tubular glands. 



General struc- Generally glands are invested externally by an 

 envelope of connecting tissue, varying in density. 

 From the deep surface of this external envelope, 

 processes or trabeculse are given off, which, traversing 

 the interior of the organ in different directions, divide 

 up the glandular parenchyma into segments (lobes, 

 lobules); they also support the vessels and nerves of 

 the organ. The vesicles and secreting tubes are 

 formed by a membrane of their own (basement mem- 



ture. 



