210 PRACTICAL HISTOLOGY fxXVIl 



tissue. This forms a coil, and hence will be seen as a 

 clump of tubes cut in various directions. The secreting 

 portion is larger in diameter than the duct, it is lined 

 by a single layer of cubical or columnar cells (a layer 

 of longitudinal fibres may be present between the cells 

 and the basement membrane). 



3. Sensory nerve-endings in stratified epi- 

 thelium. Vertical section of cornea of cat or rabbit. 

 (Gold chloride ; cp. Lesson x. 7 ; alcohol ; cut in 

 paraffin.) Observe 



The bars of the primary plexus (cp. Lesson XIV. 

 11) cut across; from this plexus small bundles of 

 fibrils run through the anterior membrane and separate 

 into a brush of fine varicose fibrils which spread out 

 immediately underneath the epithelial cells, forming 

 the sub-epithelial plexus. Probably the section in 

 some part will be a trifle oblique ; here a fragment of 

 the small meshed sub-epithelial plexus will be seen, 

 elsewhere fine fibrils will be seen running a longer or 

 shorter course underneath the cells 1 . 



The inter- epithelial nerve-fibrils seen in places 

 to arise from the sub-epithelial plexus ; they are fine 

 varicose fibrils running at first nearly straight out- 

 wards, their branches are best seen near the surface. 



The peripheral course of the nerve fibres in the 

 parts of the skin where there are no special terminal 

 organs is in the main like that described above for the 

 cornea. 



1 The sub-epithelial plexus is only seen satisfactorily in sections, 

 cut from the surface of the cornea, which include the anterior surface 

 of the basement membrane. 



