'36 



PHYSIOLOGY FOK BKCJINNKkS 



the wall of which is formed of a single layer of small cubical 

 cells, and this leads to a collection of larger cubical cells 

 surrounded by blood-vessels lying in the connective tissue 

 layer. Such a collection of cells is called a gland, and the tube 

 its duct. The mucous membrane of the whole of the ali- 

 mentary canal contains, and indeed is largely made up of, 

 glands. The simplest glands consist merely of a blind 

 tube lined by cubical cells ; such simple glands occur in 

 the wall of the stomach. Or the lower end of the tube 

 may be branched, the branches being blind and lined by more 

 or less cubical cells, and all of the branches uniting to form 



d 



n 



FlG. 60. Diagram to show the gland cells and beginning ofom: of the finest 



duels of the pancreas. 



it, Gland cells ; ;/, their nuclei ; b, the cavity or lumen into which the secretion i^ 

 paured to be carried away by the duct d. 



the single tube which proceeds outwards to the free open- 

 ing. If the lower end of the tube branches to a large extent a 

 racemose gland is formed, which consists of clusters of cubical 

 cells forming the walls of minute blind tubes, all of which 

 gradually unite into a single tube, the duct of the gland, 

 opening on the free surface. In some cases many clusters of 

 branched tubes are bound together into a large mass or organ, 

 the whole forming a large racemose gland which may have a 

 duct one or two inches long. An example of such a large 

 racemose gland is the pancreas. 



(".lands are always well supplied with blood-vessels which 

 lie close to the cells lining the deeper part of the gland. 



The function of a gland is to form from the .blood a fluid 



