40 SECRETION. 



Serous Membranes. The structure of the serous mem- 

 branes is very simple. They consist of a dense tissue of 

 fibres, which is frequently quite closely adherent to the sub- 

 jacent parts, and covered by a single layer of pavement, or 

 tesselated epithelium. The fibres are mainly of the inelastic 

 variety arranged in bundles, interlacing each other in the 

 form of a close net-work, and mingled with small, wavy 

 fibres of elastic tissue and numerous blood-vessels. It has 

 not been satisfactorily demonstrated that the serous mem- 

 branes contain nerves and lymphatics, though the latter are 

 generally quite abundant in the subjacent parts, particularly 

 beneath the visceral layers. 1 The capillary blood-vessels are 

 in the form of a close, polygonal net-work, with sharp angles. 



The epithelium of the serous membranes is pale, regular, 

 with rather large nuclei, and is easily detached after death. 

 Todd and Bowman describe a delicate basement -membrane 

 between the fibrous structure and the layer of epithelium, 2 

 but others have not been able to distinguish it, and the ex- 

 istence of such a membrane is considered doubtful. 3 



These membranes, as a rule, form closed sacs, with their 

 opposing or free surfaces nearly in apposition. The secre- 

 tion, which is generally very small in quantity, is contained 

 in their cavity. The exceptions to this are the arachnoid 

 membrane, the surfaces of which are exactly in apposition, 

 the fluid being situated beneath both layers, 4 and the perito- 

 neum of the female, which has an opening on either said for 

 the Fallopian tubes. 



Synovial Membranes. The true synovial membranes are 

 found in the diarthrodial, or movable articulations ; but in 



1 See vol. ii., Absorption, p. 433. 



2 TODD AND BOWMAN, Physiological Anatomy and Physiology of Man, Lon- 

 don, 1845, vol. i., p. 130. 



3 BRINTON, Serous and Synovial Membranes. Cyclopedia of Anatomy and 

 Physiology, London, 1847-1849, vol. iv., part i., p. 514. 



* MAGENDIE, Memoire sur un liquide qui se trouve dans le crane et le canal 

 vertebral de Vhomme et des animaux mammiferes. Journal de physiologic, Paris, 

 1825, tome v., p. 36. 



