358 SPECIAL PHYSIOLOGY. 



the palmar surface of the distal phalanx of the index finger, there are 

 about 108 on a square line, on the second phalanx 40, on the first 15; 

 on the palmar surface of the metacarpal bone of the little finge'r and 

 on the middle of the sole of the foot 8, and on the tip of the great 

 toe 14. 



The cutaneous papillae are vascular organs, serving to increase the 

 nutrient and formative surface for the generation of the constantly 

 wasting epidermis; whilst those which contain nerves, are the proper 

 organs of touch, their number, size, and complex development, being 

 in exact proportion to the perfection of this sense in different parts of 

 the skin. Two kinds of papillae have been described by Wagner, viz., 

 one containing capillary loops only, and the other being merely pro- 

 vided with nerve-fibres and axile bodies ; but, according to Kolliker, 

 the vascular papillae of the lip contain nerves, and the papillae of the 

 palm of the hand, which possess axile bodies, frequently contain capil- 

 lary loops. 



In certain situations in the subcutaneous tissue, as in the hands and 

 feet, some of the cutaneous nerve-fibres pass into curious little oval 

 bodies, varying from J^th to J^th of an inch in length, named the 

 Pacinian corpuscles. These consist of numerous concentric mem- 

 branous laminae, composed of spirally arranged fibres, and having 

 between them, spaces filled with fluid. In the centre, is an elongated 

 chamber, into which the axial part of the nerve fibre penetrates, and 

 which also contains a semi-fluid substance. The nerve fibre enters 

 these bodies at a sort of pedicle, together sometimes with a capillary 

 loop ; and then, losing its medullary sheath, becomes reduced to its 

 axis-cylinder, and penetrating to the internal chamber, ends in a little 

 bifid or trifid knob, perhaps turning back again. Similar bodies are 

 likewise found on the sympathetic plexuses of the abdomen, in man. 

 In many animals, these corpuscles are found in large numbers in 

 the feet ; they are very abundant in the skin, feet, bill, and tongue 

 of birds. They are especially well seen on the mesenteric nerves of 

 the cat. 



The nails are modified parts of the cuticle, with which they are 

 continuous along the hinder part of their edges, by their upper surface 

 near the root, and by their under surface near the tip ; hence, when 

 loosened by decomposition, they slip off from the true skin, in intimate 

 connection with the glove-like cuticle. They consist of a deep soft 

 layer, Fig. 68, 2, composed of roundish, somewhat compressed, epider- 

 moid cells and of a hard superficial stratum, 1, made up of flattened, 

 horny, and intimately adherent cells. The under concave surface of 

 the nails, is accurately moulded on to the cutis or true skin, to which 

 it is firmly adherent during life. The part of the cutis beneath the 

 nail, is called the matrix, or bed, 5 ; posteriorly, it is doubled on itself, 

 forming a semilunar groove, Fig. 68, b, or recess, into which the hin- 

 der edge or so-called root of the nail is closely set. The matrix is 

 highly vascular; it is covered with numerous vascular papillae, Fig. 

 68, a, 5, running lengthwise under the nail ; but opposite the crescendo 

 white spot seen near the root of the nail, called the lunula, the papillae 

 are smaller, less vascular, and irregularly scattered. 



