NERVE-ENDINGS. 307 



special methods, such as the gold chloride method, and the 

 methylene-blue stain, it can be demonstrated that the nerve 

 fibres which lose their sheaths at the margin of the epithelium 

 form at their ends shell-like thickenings, the so-called tactile 

 menisci. Each meniscus lies closely applied to one of the large 

 clear cells spoken of (MerkeVs tactile cells) in such a way that 

 its concave side is adjacent to the lower surface of the cell. 

 The tactile cells are to be considered as modified epithelial 

 cells, whose differentiation is initiated by the entrance of the 

 nerve fibre into the epithelium (Szymonowicz). 



As a transition form between the" free intra-epithelial nerve- 

 endings and Merkel's corpuscles may be mentioned the nerve- 

 endings found in the frog's tongue. According to the work 

 of Bethe, the nerve fibres are connected by flattened end plates 

 with specialized epithelial cells. To this class belong also the 

 nerve-endings in the mole's snout (Elmer s organ). The nerve 

 fibres in this organ enter into combination with modified 

 epithelial cells by means of lateral knob-like branches. Here 

 must also be classified the nerve-ending in the organs of taste, 

 hearing, and sight ; for in these the branched and thickened 

 ends of the nerves come into contact with the so-called sense 

 cells or neuro-epithelial cells. In the olfactory organ the rela- 

 tion is otherwise (see later). 



(2) Nerve- endings in Connective Tissue. 



Here also there are free nerve-endings found in many parts 

 of the body. The nerve fibre loses its sheaths in the con- 

 nective tissue, and the naked axis cylinder breaks up into 

 more or less numerous fine branches. Such endings are estab- 

 lished in the tendons (Golgi, Cattaneo, and others), where the 

 much-branched axis cylinder enters between the tendon bundles 

 and ends freely. They are also found in the skin under the 

 basal membrane and at the boundary between the epidermis 

 and the true skin (Ranvier, Szymonowicz); in the endocardium 

 (v. Smyrnow) ; in the hyaline membrane of the hair follicle 

 (Figs. 231, 232); in the ciliary body; in the lungs, and mother 



