XER VO US TISS C '. 



77 



skin of the lips, and the mucous membrane of the tip of the tongue, the palpebral 

 conjunctiva, and the skin of the nipple They are not found in all the papillae; 



FIG. 53. Tactile papilla of the hand treated with acetic 

 acid. Magnified 350 times. A. Side view of a papilla of the 

 FIG. 52. 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, c. 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. 



but from their existence in those parts in which the skin is highly sensitive, it is 

 probable that they are specially concerned in the sense of touch, though their 

 absence from the papillae of other tactile parts shows that they are not essential to 

 this sense. 



The Pacinian corpuscles ! (Fig. 54) are found in the human subject chiefly on 

 the nerves of the palm of the hand and sole of the foot and in the genital organs 

 of both sexes, lying in the subcutaneous tissue ; but they have also been described 

 as connected with the nerves of the joints, and in some other situations, as the 

 mesentery of the cat and along the tibia of the rabbit. Each of these corpuscles 

 is attached to and encloses the termination of a single nerve-fibre. The corpuscle, 

 which is perfectly visible to the naked eye (and which can be most easily demon- 

 strated in the mesentery of a cat), consists of a number of lamellae or capsules, 

 arranged more or less concentrically around a central clear space, in which the 

 nerve-fibre is contained. Each lamella is composed of bundles of fine connective- 

 tissue fibres, and is lined on its inner surface by a single layer of nucleated endo- 

 thelial cells. The central clear space, which is elongated or cylindrical in shape, 

 is filled with a transparent material, in the middle of which is the single medullated 

 fibre, which traverses the space to near its distal extremity. Here it terminates 

 in a rounded knob or end, sometimes bifurcating previously, in which case each 

 branch has a similar arrangement. Todd and Bowman have described minute 

 arteries as entering by the sides of the nerves and forming capillary loops in the 

 intercapsular spaces, and even penetrating into the central space. Other authors 

 describe the artery as entering the corpuscle at the pole opposite to the nerve- 

 fibre. 



Herbst has described a somewhat similar " nerve-ending " to the Pacinian cor- 

 puscle, as being found in the mucous membrane of the tongue of the duck and 

 in some other situations. It differs, however, from the Pacinian corpuscles, in 

 being smaller, its capsules thinner and more closely approximated, and especially 

 in the fact that the axis-cylinder in the central clear space is coated with a con- 

 tinuous row of nuclei. These bodies are known as the corpuscles of Herbst. 



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 



1 Often called in German anatomical works " corpuscles of Vater." 



