SENSORY NERVE-ENDINGS. 169 



inclosed in an investing capsule which forms a structural part of 

 the ending. 



2. Encapsulated Endings. In which the telodendrion or several 

 telodendria are surrounded by an investing capsule which separates 

 them more or less completely from the surrounding tissue. 



1. Free sensory nerve-endings are found in all epithelial tis- 

 sues and in fibrous connective tissue of certain regions. A sensory 

 nerve-fiber terminating in such an ending usually proceeds without 

 branching to near its place of termination, where, while yet a 

 medullated fiber, it branches and rebranches a number of times, 

 always at the nodes of Ranvier, the resultant branches diverging at 

 various angles. If the free sensory endings are in epithelial tissue, 

 these larger medullated branches are situated in tne connective- 

 tissue mucosa under the epithelium. From these larger medullated 

 branches, are given off smaller ones, also medullated, which may 

 divide further, and which pass up toward the epithelium, and near its 

 under surface divide into nonmedullated branches. Nonmedullated 

 branches are also given off from the medullated ones as they 

 approach the epithelium, leaving the parent fibers at the nodes of 

 Ranvier. Many of the nonmedullated branches thus formed, after 

 coursing a variable distance under the epithelium, enter it and break 

 up into numerous very small branches, which, after repeated divi- 

 sion, terminate between the epithelial cells in small nodules or 

 discs of variable size and configuration. The small branches result- 

 ing from a division of one of the larger nonmedullated branches 

 constitute one of the terminal telodendria or end-branches of the 

 dendrites of peripheral sensory neurones terminating in free sensory 

 nerve-endings. In fibrous connective tissue the same general 

 arrangement of the branches prevails. In figure 135 is shown the 

 peripheral distribution of the dendrite of a peripheral sensory 

 neurone terminating in a free sensory nerve-ending. 



2. Encapsulated Sensory Nerve-endings. These nerve-end- 

 ings may be divided into two quite distinct groups, such as have a 

 relatively thin fibrous-tissue capsule, 



containing mainly telodendria of the 

 nerve or nerves terminating therein, 

 and such as have a distinctly lamel- 

 lated, fibrous tissue capsule, usually 

 investing, besides the nerve-termi- 

 nation, other tissue elements. To 

 the former group belong three types 

 of sensory nerve - endings, which, 

 owing to their similarity of struc- 

 ture, may be described together. 



T-, J ^ i i 11 r -tr Fig. 136. End-bulb of Krause 



These are the end-bulbs of Krause, f rom conjunctiva of man ; methylene- 



Meissner's tactile corpuscles, and blue stain (Dogiel, "Arch. f. mik. 

 the genital corpuscles. They have Anat '" vo1 ' XXXVII ) 

 all been investigated recently by 



