280 MANUAL OF HISTOLOGY. 



sheath, and afterward continue their course as non-medullated 

 fibres. The nerve-bundles pass upward in a more or less oblique 

 direction from the subcutaneous connective tissue through the 

 corium to the subpapillary network of blood-vessels, around 

 which they form a plexus. From this subpapillary plexus 

 medullated fibres run upward and pass into the tactile cor- 

 puscles. 



The non-medullated nerve-fibres form a reticulum around 

 the blood-vessels of the pars reticularis corii and the capilla- 

 ries of the papillae. They consist of thick or fine, smooth, 

 varicose fibres with numerous nuclei. These fibres proceed 

 from the network around the subpapillary blood-vessels up- 

 ward toward the rete Malpighii, and either pass directly into 

 the rete or run for a short distance parallel to its under sur- 

 i'ace, and then finally enter that layer. Within the epider- 

 mis the fibres run between the cells and terminate in a manner 

 not yet definitely known. Their mode of division and termina- 

 tion within the epidermis is probably similar to that occurring 

 in the cornea. Within the papillae the nerve-fibres frequently 

 divide before entering the rete. 



The manner of distribution and termination of the non- 

 medullated nerve-fibres can only be studied successfully in tis- 

 sue stained with gold chloride. The tissue must be fresh, and 

 a weak solution of the gold chloride used. When sufficiently 

 stained the tissue is placed in -distilled water slightly acidu- 

 lated with acetic acid and exposed to the light. 



The Pacinian corpuscles are found in greatest abundance in 

 the skin of the fingers, toes, palm of the hand, sole of the foot, 

 but also occasionally in other regions of the skin. Their struc- 

 ture is described in the article on the nervous system. 



Tactile corpuscles. As already mentioned, some of the 

 medullated nerve-fibres forming the plexus surrounding the 

 subpapillary blood-vessels, pass upward and enter the so-called 

 tactile corpuscles. These corpuscles are generally seated in the 

 papillae, but occasionally they are found in the subpapillary 

 region, i.e., the upper part of the corium. The majority of 

 the papillae containing such corpuscles have no blood-vessels. 

 They are more or less oval in form, and can be easily recog- 

 nized under the microscope by their dark contours and by the 

 oblique lines produced by the transversely running connective- 

 tissue fibres of the outer surface of the corpuscle. There may 



