THE HAIR. 261 



an oval section, or some form differing still more from circular. 

 (Fig. 161, a, b.) Those of the scalp are the most nearly cylindrical 

 in form. Nor are they of equal diameter throughout; but fusiform 

 rather, and usually terminating in a very acute point. Indeed, 

 hairs cut off transversely, become pointed again in a short time; 

 apparently by the wearing away of the more external portions of 

 the fibrous substance. 



The number of hairs upon a given extent of surface varies with 

 their color and the particular part of the body. On the same ex- 

 tent of surface, Withof found 147 black hairs, 162 brown, and 182 

 blonde. On a surface one-fourth of an inch square, he found in 

 case of a moderately hairy man, 293 hairs upon the scalp, 39 on 

 the chin, 34 on the pubes, 23 on the forearm, 19 on the outer mar- 

 gin of the back of the hand, and 13 on the anterior surface of the 

 leg. In men, closely set hairs not unfrequently occur on the chest, 

 shoulders, and extremities. At the period of puberty, a sudden 

 development occurs in both sexes upon the pubes and axillae ; and 

 in males on the chin, cheeks, abdomen, and chest also. In a very 

 hairy man, mentioned by Wilson, 1 52 hairs were found on a certain 

 surface on the chin, and 45 on the pubes. Being married soon 

 after, there were found, at the end of four years, 59 on the chin and 

 50 on the pubes. On all other parts of the body the hairs were 

 diminished. 



The hairs are implanted either singly or in twos and threes, or 

 even four or five together. The last is the rule in the foetus, and, 

 so far as the lanugo is concerned, in the adult also. The direction 

 of the hairs and hair-sacs, is seldom perpendicular to the skin, but 

 oblique ; they being arranged in curved lines which either converge 

 towards certain points or lines, or diverge from them in two or more 

 directions. Hence result a variety of figures, which Eschricht 

 termed " streams, whorls, and crosses ;" which are easily made out 

 on the median line of the back, chest, and abdomen, on the line 

 between the thorax and the abdomen, in the axilla, on the scalp, at 

 the internal angle of the eye, and on the elbow. The natural di- 

 rection of the hairs is, in general, downwards, as shown especially 

 on the various parts of the head. It may, however, here be changed 

 by persevering efforts. Yery rarely, two hairs are found implanted 

 in the same hair-sac. 



1 Treatise on the Skin. 



