Page:The American Cyclopædia (1879) Volume VIII.djvu/397

 HAIR 383 the size ia greatest toward the lower third, the root being smaller and the end terminating in a point. The hairs of the head are the longest, those of the beard the thickest, and those of the general surface the finest ; among women the hair of the head has been known to fall be- low the feet, and the beard of man occasionally reaches to the waist ; frequent cutting and sha- ving of hairs increase their thickness, but not necessarily their number. Hairs are observed in the foetus as early as the third or fourth month, in the order of follicle, bulb, and hair. From the resemblance the mucous meni- es to the skin, it is t surprising that hairs sometimes devel- onthe conjunctiva of the eye, in the intes- tines, ovaries, &c. ; they frequently found in lysted tumors and in r inversions of epi- rmic structure. Hairs ay be transplanted, and will contract organ- ic adhesion in the new ues ; according to le, a hair which has bed its full develop- ent becomes contract- just above the bulb falls off. In vigor- s health the hairs are ick and firmly set in e skin ; in debilitated
 * rsons they fall out

ntaneously or with "ery slight force ; in e latter case the bulb nerally alone comes ay, the sheath and remaining behind, d capable of reprodu- the hairs under per treatment or fa- >rable circumstances; when the entire licles are removed, is possible that new es with their germs ay be formed ; new hafts are constantly in cess of formation, as shown by the short d pointed hairs on e scalp of old persons. The nutrition of airs is effected through vessels in close contact ~ith their tissue, without entering into their cture ; so that causes affecting the gen- health, and especially the condition of the in, act powerfully upon the nutrition of the ir ; the premature baldness and grayness of Americans as a people is in great measure 385 VOL. vm. 25 A Hair in its Hair Sac. shaft of hair above the skin ; &, cortical substance of the shaft, the medulla not being visible ; c, new- est portion of hair grow- ing on the papilla (i) ; <?, cuticle of hair; e, cavity of hair sac ; ./, epidermis (and root sheaths) of the hair sac corresponding to that of the integument (in) ; (7, diA'ision between dermis and epidermis ; h, dermis of hair sac corre- sponding to dermis of in- tegument (T) ; Jc, mouths of sebaceous glands ; n, horny epidermis of in- tegument. owing to the non-observance of hygienic rules, and to excess of mental and physical labor in a climate foreign to the race. Hairs are distrib- uted over the entire surface of the human body except the palms, soles, and terminal joints of the fingers and toes ; but for special purposes most abundantly on the scalp, brows, edge of the lids, pubis, chin, cheeks, armpits, chest, and entrance of the nose and ears. In these situations the number varies according to tem- perament, age, health, and sex. According to Withof, the quarter of a square inch contained 293 hairs on the head, 39 on the chin, 23 on the forearm, 19 on the back of the hand, and 13 on the front of the thigh ; in the same extent he counted 147 black, 162 brown, and 182 flaxen hairs, showing the comparative fine- ness. Long and strong hairs are often found growing from moles and neevi in various parts of the body. The hair generally grows in an oblique direction on account of the way in which the follicles are placed ; these are sometimes placed wrongly on tlje scalp, causing much trouble to anxious mothers; perseverance will generally bring the refrac- tory locks into the desired direction. From contraction or corrugation of the skin from cold, fear, or other causes, the hair, especially on the head, becomes partially erect, though it can never stand on end "like quills upon the fretful porcupine." The color of the hair de- pends partly on the presence of pigment gran- ules, and partly on the existence of numerous minute air spaces which cause it to appear dark by transmitted light ; its intensity gener- ally bears a close relation to the color of the iris and the skin ; in albinos and in gray-haired persons the coloring matter is deficient or ab- sent. Long contact with chlorine decolorizes hair; and the undoubted fact that hair may turn white in a short time under the influence of strong emotions is doubtless to be explained by some chemical action upon the oily coloring matter, as suggested by Dr. D. F. Weinland, and more fully explained in the article FEATH- ERS. The turning gray of the hair is no sign of its loss of vitality, as hair of this color often grows for years as vigorously as the darker hued. Hair is remarkable for strength, elas- ticity, and durability, the first depending on its fibrous structure and the last two on its horny nature ; a single hair will bear a strain of 1,150 grains. Hairs will endure not only during a long life, but will grow after death, and last for centuries. It is well known that hairs, especially of cats and other animals, be- come electrical by rubbing; the hygroscopic property of hair has been painfully manifested to many a beau and belle whose rebellious locks have refused to retain their artistic curl on the sudden occurrence of a moist atmos- phere. Nitrate of silver blackens hair, form- ing a sulphuret, and this substance and sulphur form the bases of most of the popular hair dyes. When burned, hair emits a disagree- able odor as of burning horn. The uses of