468 



SECRETING GLANDS. 



[OH. xxix. 



the lymph whichbathes them the necessary material and trans- 

 form it into the secretion which they pour into the cavity. 



The principal secreting organs are the following : (i) the 

 serous and synovial membranes ; (2) the mucous membranes with 

 their special glands, e.g., the buccal, gastric and intestinal glands ; 

 (3) the salivary glands and pancreas ; (4) the mammary glands ; 

 (5) the liver; (6) the lacrimal gland; (7) the kidney *and skin; 

 and (8) the testes. 



Serous membranes. We have already discussed the struc- 



Fig. 391. Section of synovial membrane, a, epithelial covering of the elevations of the 

 memhrane ; 6, underlying tissue containing fat and blood- vessels ; c, ligament covered 

 by the synovial membrane. (Cadiat.) 



ture of serous membranes (p. 204), and also the question whether 

 the lymph is a true secretion (pp. 317 320). 



The synovial membranes line the joints and the sheaths of 

 tendons and ligaments with which we may include the synovial 

 bursae. The contents of these sacs is called synovia; it lubricates 

 the surfaces of the joint and so ensures an easy movement. 

 Synovia is a rich lymph plus a imicinoid material ; and it is this 

 latter constituent which gives the secretion its viscidity. It is 

 thus a true secretion ; and is formed by the epithelial cells which 

 form an imperfect lining to the sac. and which are especially accu- 

 mulated on the processes of the synovial fringes (fig. 391). 



