ae 
730 THE SKIN OR INTEGUMENT. 7 
from which delicate fibrils pass between the cells of the rete mucosum, where. 
they become beaded, and end in rounded swellings or flattened dises—the tactile 
discs of Ranvier. 
The special end organs are of three chief varieties (Fig. 558): (a) Corpuscula 
bulboidea (Krausi1), found on the lips, glans penis, etc., and consisting of a connective 
tissue capsule enclosing a core of elongated and polygonal cells, amongst which the 
axis-cylinder of the nerve fibril becomes branched and its ramifications end in clubbed 
extremities. (6) Corpuscula lamellosa (Vateri and Pacini). These are small, oval 
bodies, with a long diameter of 2 to 5 min., and are found in the subcutaneous 
tissue attached to the nerve trunks. They are very numerous on the digital 
nerves, but are present in many other situations, e.g. in the mesentery. Hach 
possesses a sheath, consisting of a number of concentrically-arranged connective 
tissue lamellie, covered by endothelium continuous with the perineurium. The 
central part of each corpuscle consists of a soft, almost homogeneous core. The 
nerve tibre passes along 
the centre of the stalk of 
the corpuscle, and, reach- 
ing the core, loses its med- 
wary sheath, whilst its 
axis-cylinder passes into 
the core and becomes 
branched near its distal 
extremity, the branches 
ending in bulbous enlarge- 
ments. (¢) Corpuscula 
tactus (Meissneri). These 
are very numerous on the 
flexor aspect of the hands 
and feet, and especially so 
in the skin over the 
Fic. 588.—TactiLeE CoRPUSCLES. terminal phalanges; but 
A, End bulb (Krause). they also exist in other 
Gece tole Ge tietaeoety (atteenmanier) parts of the body. They 
occupy certain of the 
papille of the corium, and are oval in shape, their long diameter in the hand 
being from 110, to 160. They consist of a connective tissue capsule, which 
sends imperfect septa into the interior of the corpuscle. One or two nerve fibres 
perforate the capsule, either directly or after taking a spiral course around it; and 
losing, as a general rule, their medullary sheath, their axis-cylinders break up into 
fibrils, which end in globular or discoid enlargements. 
Ruffini has described a special variety of terminal corpuscle in the human finger. They are 
termed Ruffini’s endings, and are situated either at the junction of the corium and subcutaneous 
tissue, or are embedded in the latter. Of an oval shape, they consist of a connective capsule 
within which the axis cylinder divides into varicose filaments, and these terminate in small 
knobs. 
APPENDAGES OF THE SKIN. 
The appendages of the skin comprise the nails, the hairs, the sebaceous and 
the sudoriparous or sweat glands. 
Nails.—The nails or ungues (Figs. 539, 540) are epidermal structures, and, in 
man, represent the hoofs and claws of the lower animals. The root of the nail, or 
radix unguis, is hidden from view and embedded in a fold of skin; the body (corpus 
unguis) or uncovered part, rests on the corium and ends in a free edge or margo 
liber. The greater part of the lateral margins is overlapped by a duplicature 
of skin, termed the nail-wall or vallum unguis. The nails are pink in colour, with 
the exception of a small semilunar area near the root, which is more opaque than 
the rest and is named the lunula. The lunule diminish in size from the thumb 
towards the little finger, while the thickness of the nail diminishes towards its root 
and lateral margins. The corium under the nail is highly vascular and sensitive, 
