ORGANS OF SENSE. 149 
continuous with the nail a little beyond its root and lateral borders, and is 
also continued from the back of the pulpy end of the finger to its concave 
surface near the end or free edge; as the nail is thus continuous with the 
cuticle, so is the matrix with the adjoining cutis. The nails not only protect 
the sensitive ends of the fingers, but aid them as instruments of prehension, 
as well as in various manual operations; they also afford a firm point of 
support behind the tactile papillae, which is of essential service in the exer- 
cise of touch. 
4, Tue Hairs. These cutaneous appendages, like the epidermis and nails, 
are insensible and non-vascular; they exist in all parts of the body except 
the palms of the hand and soles of the feet, varying very much in strength, 
form, color, and extent, in different situations. On the greater portion of 
the body, they are short, soft, and downy; on the head, in the eyelids, 
axilla, and on the pubic region, they are much longer and stronger; the 
extent, however, of their development varies with the age, sex, and tempera- 
ment of the individual. The loose or projecting portion of a hair is called 
the shaft; the root is fixed in a follicle composed of an involution of the 
cuticle and of the superficial lamina of the cutis; this follicle is depressed 
through the cutis, enlarges into a pyramidal or bulbous form, and is 
imbedded in the areolar or adipose tissue, from which it receives its vessels, 
and in which it isso firmly implanted as not to be disturbed by pulling out 
the hair. The whole follicle is lined by the involuted skin, and at the 
bottom the cutis presents a highly vascular papilla or pulp, which secretes 
the matter of the hair. Thus the vessels of the pulp give out the lymph 
containing cell germs; these become cells with nuclei, and are gradually 
condensed and elongated into a scaly fibrous substance which is continually 
pushed forwards by additions from beneath, and escapes through the open- 
ing in the epidermis, generally in a slanting manner. The cells forming 
this outer surface or cortex of the hair are flat and hard, and inclose a 
more loose fibrous texture named the medulla or pith; these external scales 
are successively produced, the last formed overlapping the preceding. 
Owing to the less density of the internal cells, the hair when magnified has 
a cellulo-tubular appearance. ‘Thus the hair is nothing but cuticle specially 
modified by the papilla on the cutis vera at the bottom of the follicle. Pi o- 
ment granules are also intermingled with and adherent to the cells at the 
root of each hair; on these the color of the hair depends. Into the hair 
follicle one or more sebaceous ducts open, the secretion of which lubricates 
the hair and imparts to it its oily character. 
5. THE SUBCUTANEOUS CELLULAR TISSUE is a soft, extensile substratum 
of the skin, composed of contractile fibres and plates of cellular membrane. 
It serves to connect the skin with the subjacent fascia, and to conduct ves- 
sels and nerves to the true skin; it incloses angular cavities or spaces inter- 
communicating freely, and filled during life with a watery exhalation. 
6. THE ADIPOSE TISSUE at one time was supposed to be identical with 
cellular. It is, however, characterized by consisting of numerous short sacs 
having no opening or communication, each sac being a delicate simple 
membrane, supplied with blood-vessels and secreting from its cavity the 
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