58 FIFTH LECTURE. 



7. The corium. More firmly interwoven, decussating con- 

 nective-tissue bundles with numerous elastic fibres. The 

 closely interwoven, very vascular tissue projects towards the 

 surface in small papillae of varying shape, in the form of the 

 tactile bodies. It is continuous below, without any sharp 

 demarcation, with the subcutaneous cellular tissue. Other 

 foreign constituents consist of hairs, involuntary muscles, 

 glands, nerves. As a covering, we are already familiar with 

 the epidermis, the thickest pavement epithelium of the body 



(P- 32). 



8. The mucous membranes. Also extremely vascular, but 

 less compactly arranged, and with fewer elastic elements. 

 In places it is enormously rich in glands. Smooth muscles 

 form a widely diffused constituent. The surface frequently 

 projects in papillae. The ordinary connective tissue of the 

 mucous membranes may, however, be replaced by reticular 

 connective tissue (p. 47). We already know that the epithe- 

 lial covering differs exceedingly (pp. 30, 33, and 34). 



9. The vascular membranes of the central nervous organs 

 and of the eye ; that is, the pia mater, choroidal plexus and 

 choroid. A thin, soft connective tissue, in the choroid a 

 reticulum of pigmented cells, here shows throughout an enor- 

 mous wealth of blood-vessels. 



10. In the structure of the vascular zualls connective tissue 

 plays an important role. Nevertheless, the elastic element 

 often increases to such an extent, that the connective-tissue 

 bundles and cells recede. One speaks then of "elastic" 

 tissue. 



11. This predominance of the elastic elements is also pre- 

 sented by the ligaments and membranes of the respiratory 

 organs, and likewise by the tissue of the lungs. The same is 

 also seen in the outer layer of the oesophagus, the yellow 

 ligaments of the vertebral column, and the ligamentum 

 nuchae of mammalial animals. Many of the latter structures 

 have lost all connective-tissue bundles. 



Connective tissue possesses but slight vital dignity ; it 

 comes into consideration in the structure of the organism, in 



