204 MUCOUS MEMBll AISLES. 



Lymjiliatic vessels have not hitherto been demonstrated in the 

 synovial membranes. 



" Herves. — W, Krause describes the nerves of the sjTiovial membranes 

 (at least those of the joints) as terminating in peculiar corpuscles allied 

 to end bulbs. Another observer (Nicoladoni) has traced the nerves into 

 a plexus of pale fibrils lying close under the surface of the membrane. 



Development. — Reyher describes the development of the synovial mem- 

 Ijianes as follows : — At the time of the fomiation of a joint the surrounding- 

 tissue becomes changed, so that while its outer jiart developes into the fibrous 

 capsule of the joint, its inner part fonns the commencement of the synovial 

 membrane. The cartilage cells on the surfaces of the newly formed joint are at 

 first placed closely together without matrix or intercellular substance ; after a time 

 this appears in fine lines between the cells, so that these, in silvered preparations, 

 now present an epithelioid appearance. By a fm-ther develoi^ment of intercellu- 

 lar substance the superficial cells become more sei^arated from one another, and 

 now possess an irregularly branched shape with communicating processes. Near 

 the edge of the cartilage this condition is permanent, so that the marginal zone 

 of the sjaiovia] membrane is formed here hi altu from what was originally carti- 

 lage. More towards the centre of the articular surface, however, a further 

 change takes place in the progress of development, for in these parts the cells 

 lose their processes and acquire the characters of ordinary cartilage cells, whilst 

 at the same time the matrix becomes much increased between them, and forms 

 also a thin layer covering their sui-face. 



Synovia. — As already stated, this is a viscid transparent fluid ; it has a yellowish 

 or faintly reddish tint, and a slightly saline taste. According to Frerichs, the 

 synovia of the ox consists of 9-l"85 water, 0'56 mucus and cells. Ot)7 fat, 

 ."•51 albumin and extractive matter, and O'DO salts. If a di'op of sjmovial fluid 

 be examined microscopically, it is found to contain (in addition to fat-molecules) 

 a few amoeboid corpuscles, as well as cells similar to those which occiu" on the 

 surface of the membrane. 



MUCOUS MEMBRANES. 



These membranes, unlike the serous, line internal passages, and other 

 cavities which open on the surface of the body, as well as various re- 

 cesses, sinuses, gland-ducts and receptacles of secretion, which open 

 into such passages. They are habitually subject to the contact of 

 foreign substances introduced into the body, such as air and aliment, 

 or of various secreted or excreted matters, and hence their surface is 

 coated over and protected by mucus, a fluid of a more consistent and 

 tenacious character than that which moistens the serous membranes. 



Distribution. — The mucous membranes of several different or 

 even distant parts are continuous, and they may all, or nearly 

 all, be reduced to two great divisions, namelj^ the (jastro-jmcumonic 

 and gpnito-unnanj. The former covers the inside of the alimentary 

 and air-passages as well as the less considerable cavities com- 

 municating with them. It may be described as commencing at 

 the edges of the lips and nostrils, where it is conthiuous with 

 the skin, and proceeding through the nose and mouth to the 

 throat, whence it is continued throughout the whole length of the ali- 

 mentary canal to the termination of the intestine, there again meeting 

 the skin, and also along the windpipe and its numerous divisions as far 

 as the air-cells of the lungs, to which it affords a lining. From the 

 nose the mcmlirane may be said to be prolonged into the lachrymal 

 passages, extending up the nasal duct into the lachrymal sac and along 



