THE NERVOUS TISSUE. 



1121 



with one another, thus forming a network. This network passes between the 

 elements of the tissue to which the nerves are distributed, which is always 

 epithelial, the nerve-fibrils lying in the interstitial substance between the epithelial 

 cells, and there terminating, though some observers maintain that the actual ter- 

 minations are within the cells. In this way nerve-fibres have been found to ter- 

 minate in the epithelium of the skin and mucous membranes, and in the anterior 

 epithelium of the cornea. 



The end-bulbs of Krause (Fig. 657) are minute cylindrical or oval bodies, con- 

 sisting of a capsule formed by the expansion of the connective-tissue sheath of a 

 medullated fibre, and containing a soft semifluid core in which the termination of 

 the axis-cylinder is situated, ending either as a bulbous extremity, or in a coiled- 

 up plexiform mass. End-bulbs are found in the conjunctiva of the eye, where 

 they are spheroidal in shape in man, but cylindrical in most other animals, in the 

 mucous membrane of the lips and tongue, and in the epineurium of nerve-trunks. 

 They are also found in the genital organs of both sexes, the penis in the male, 

 and the clitoris in the female. In this situation they have a mulberry-like 

 appearance, from being constricted by connective-tissue septa into from two to 

 six knob-like masses, and have received the name of genital corpuscles. Very 

 similar corpuscles are found in the epineurium of nerve-trunks. In the synovia! 

 membrane of certain joints (e. g., those of the fingers), rounded or oval end-bulbs 

 have been found ; these are designated articular end-bulbs. 



Tactile corpuscles have been described by Grandry as occurring in the papillae 

 of the beak and tongue of birds, and by Merkel as occurring in the papillae and 

 epithelium of the skin of man and animals, especially in those parts of the skin 

 devoid of hair. They consist of a capsule composed of a very delicate, nucleated 

 membrane, and contain two or more granular, somewhat flattened cells, between 

 which the medullated nerve-fibre, which enters the capsule by piercing its investing 

 membrane, is supposed to terminate. 



FIG. 658. Tactile papilla of the hand treated with acetic 

 acid. Magnified Hf.O times. A. Side view of a papilla of the 

 FIG. 657. End-bulb of Krause. a. Medul- hand; a. Cortical layer. 6. Tactile corpuscle, with transverse 



lated nerve-fibre, b. Capsule of corpuscle. nuclei, c. Small nerve of the papilla, with neurilemma. d. 



(From Klein's Elements of Histology.) Its two nervous fibres running with spiral coils around the 



tactile corpuscle, e. Apparent termination of one of these 

 fibres. B. A tactile papilla seen from above, so as to show 

 its transverse section, a. Cortical layer, b. Nerve-fibre, c. 

 Outer layer of the tactile body, with nuclei, d. Clear 

 interior substance. 



The tactile corpuscles (Fig. 658), described by Wagner and Meissner, are oval- 

 shaped bodies, made up of connective tissue, and consisting of a capsule, and 

 imperfect membranous septa, derived from it, which penetrate its interior. The 

 axis-cylinder of the medullated fibres passes through the capsule, and having 

 entered the corpuscle terminates in a small globular or pyriform enlargement, near 

 the inner surface of the capsule. These tactile corpuscles have been described as 

 occurring in the papillae of the corium of the hand and foot, the front of the 



