20 GENERAL ANATOMY OF THE SEROUS MEMBRANES. 



vena cava passes through an aperture in the tendinous centre 

 of the diaphragm to unite itself to the right auricle of the 

 heart. 



General Anatomy of Serous Tissues. 



The serous tissue, is found in every part of the body where 

 there is an habitual movement of parts upon each other. Its 

 object appears to be to diminish friction and to facilitate motion, 

 by the glassy smoothness of the Jree surfaces which it presents, 

 and by its pouring out continually a lubrifying liquid between 

 the surfaces where motion occurs. The serous system consists 

 of a great number of membranes, forming closed sacs,* which 

 are adherent by their external surface to the organs which they 

 line ; their internal surface is free and smooth, and secretes a 

 fluid, with which they are in a healthy state constantly mois- 

 tened, analogous to the serum of the blood. The adhesion of 

 the outer surface of the serous tissues to the subjacent parts, is 

 so intimate in most places, that it has only been within latter 

 times, by the labors of Bonn, Monro, and Bichat, that their 

 proper character has been determined. They consist of the 

 peritoneum, the pleura, the pericardial lining membrane, the 

 arachnoid of the brain and spinal marrow, the tunica vaginalis 

 testis, and the synovial capsulesf of the joints and tendons. 

 The serous membranes are all extremely thin, delicate and of 

 a transparent whiteness ; they are attached to the parts they 

 cover by the intermedium of cellular tissue, which in some parts 

 is long and loose, and in others so short and dense as to be 

 scarcely discernible and to which they seem to form a simple 

 serous facing. Hence Bordeu, and Rudolphi were disposed to 

 consider the serous membranes as a modification of cellular 

 tissue, formed by the flattening of the cells of the latter. 

 Though this is true probably in regard to their ultimate struc- 



* The peritoneum of the female, which has the fallopian tube opening into 

 its cavity, is the only instance of a serous membrane which is not a closed sac, 

 provided it be admitted that the synovial capsules of the joints coyer the artic- 

 ular cartilages. p. 



f The synovial membranes were considered by Bichat as forming a distinct 

 tissue, which he named synovial. P. 



