74 GENERAL ANATOMY OF THE TISSUES. 



trabecular network. In the cornea we find a modification, 

 inasmuch as the connective tissue is transparent, contains 

 fine elastic tissue in a more embryonic state, and when boiled 

 in water yields chondrin, and not gelatine. 



d. The serous membranes consist of a connective tissue, rich 

 in fine elastic fibres, whose bundles anastomose, or are inter- 

 woven in different modes ; and sometimes also, especially at the 

 surface of these membranes, appear more homogeneous. The 

 serous membranes, which never possess glands, and upon the 

 whole but few vessels and nerves, line the cavities which con- 

 tain the viscera, and present an inner surface, which is smooth 

 and shining from the presence of an epithelial investment. 

 They do not necessarily form closed sacs, as was formerly 

 believed, but may have apertures in certain localities (abdo- 

 minal aperture of the Fallopian tubes), or may be wholly 

 wanting, as upon the articular cartilages ; or the areolar 

 foundation may be absent, as in the so-called external lamina 

 of the arachnoidea cerebri. To these membranes belong, 1 , 

 the true serous membranes, as the arachnoidea, the pleura, the 

 pericardium, the peritonaeum, and the tunica vaginalis propria, 

 which all, normally, secrete only a minute quantity of serous 

 fluid ; and 2, the synovial membranes or capsules of the 

 joints, bursa mucosae, and tendinous sheaths, which afford a 

 viscid yellow secretion, — the synovia — containing albumen and 

 mucus. 



e. The corium consists of a dense network of bundles of 

 connective tissue, which at the surface, and in the papillae, 

 gives place to an indistinctly fibrillated, in part even more 

 homogeneous tissue, and contains a great quantity of finer and 

 coarser elastic networks, as well as very numerous vessels and 

 nerves. 



The corium supports the papillae upon its outer surface, and 

 is here covered by the epidermis, in connection with which it 

 forms the external skin ; from the deeper parts it is separated 

 by a soft tissue, generally very rich in fat, the subcutaneous 

 connective tissue, adipose membrane, or panniculus adiposus. 



f. The mucous membranes essentially consist of a very 

 vascular basis of connective tissue, well supplied with 

 nerves, — the proper mucous membrane — of an epithelial 

 layer covering it, and of a submucous areolar tissue, which 



