Henry Gray (18251861). Anatomy of the Human Body. 1918.
The end-bulbs of Krause(Fig. 934) are minute cylindrical or oval bodies, consisting of a capsule formed by the expansion of the connective-tissue sheath of a medullated fiber, and containing a soft semifluid core in which the axis-cylinder terminates either in 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 penis and the clitoris, and have received the name of genital corpuscles; in these situations they have a mulberry-like appearance, being constricted by connective-tissue septa into from two to six knob-like masses. In the synovial membranes of certain joints, e. g., those of the fingers, rounded or oval end-bulbs occur, and are designated articular end-bulbs.
The tactile corpuscles of Grandry occur in the papillæ of the beak and tongue of birds. Each consists of a capsule composed of a very delicate, nucleated membrane, and contains two or more granular, somewhat flattened cells; between these cells the axis-cylinder ends in flattened disks.
The Pacinian corpuscles(Fig. 935) are found in the subcutaneous tissue on the nerves of the palm of the hand and sole of the foot and in the genital organs of both sexes; they also occur in connection with the nerves of the joints, and in some other situations, as in the mesentery and pancreas 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 fiber. The corpuscle, which is perfectly visible to the naked eye (and which can be most easily demonstrated in the mesentery of a cat), consists of a number of lamellæ or capsules arranged more or less concentrically around a central clear space, in which the nerve fiber is contained. Each lamella is composed of bundles of fine connective-tissue fibers, and is lined on its inner surface by a single layer of flattened epithelioid cells. The central clear space, which is elongated or cylindrical in shape, is filled with a transparent core, in the middle of which the axis-cylinder traverses the space to near its distal extremity, where it ends in one or more small knobs. 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.
FIG. 935 Pacinian corpuscle, with its system of capsules and central cavity. a. Arterial twig, ending in capillaries, which form loops in some of the intercapsular spaces, and one penetrates to the central capsule. b. The fibrous tissue of the stalk. n. Nerve tube advancing to the central capsule, there losing its white matter, and stretching along the axis to the opposite end, where it ends by a tuberculated enlargement. (See enlarged image)
FIG. 936 Papilla of the hand, treated with acetic acid. Magnified 350 times. A. Side view of a papilla of the hand. a. Cortical layer. b. Tactile corpuscle. c. Small nerve of the papilla, with neurolemma. d. Its two nervous fibers running with spiral coils around the tactile corpuscle. e. Apparent termination of one of these fibers. B. A tactile papilla seen from above so as to show its transverse section. a. Cortical layer. b. Nerve fiber. c. Outer layer of the tactile body, with nuclei. d. Clear interior substance. (See enlarged image)