170 SPECIAL HISTOLOGY. 



the hairs on the face, trunk, and extremities, also those of the 

 caruncula lachrymalis, and those (frequently absent) of the labia 

 minora (Henle). 



The number of hairs upon a given extent of surface varies 

 very much, depending especially upon age, sex, and the colour 

 of the hairs. According to Withof, on a surface of \a'' there 

 were found 1-17 black, 162 brown, 182 fair hairs. In a moder- 

 ately hairy man, he found on \o" 293 upon the scalp, 39 on 

 the chin, 34 on the pubis, 23 on the fore arm, 19 upon the 

 outer margin of the back of the hand, 13 on the anterior 

 surface of the leg. In men, closely set hairs occur not unfre- 

 quently upon the chest, shoulders, and extremities. 



The hairs are placed either singly, or in twos and threes, even 

 four and five together. The latter is the rule in the foetus, 

 but the same disposition obtains also in adults, especially in 

 the lanugo. As Osiander and especially Eschricht, have shown, 

 the direction of the hairs and hair-sacs is rarely straight, 

 but oblique, and in different degrees in different parts of the 

 body, as may be demonstrated with ease in the hairs of em- 

 bryos, and, though less obviously, in adults also. The 

 regularity depends on this, that the hairs being arranged in 

 curved lines, which converge towards either certain points or 

 certain lines, or diverge from them in two or more directions; 

 there result a multitude of figures, which may with Eschricht be 

 denominated "streams," "whorls," and "crosses." Streams with 

 converging hairs are found, for example, in the median line of 

 the back, chest, and abdomen, in the line which answers 

 to the ridge of the tibia, &c. &c. ; streams with diverging 

 hairs occur on the line between the thorax and abdomen, on 

 the one hand, and the back on the other, &c. ; whorls and 

 crosses with diverging hairs are found in the axilla, on the scalp, 

 at the internal angle of the eye ; with converging hairs, on the 

 elbow. For further details I must refer to Eschricht's figures 

 and descriptions, concerning which, however, it is to be re- 

 marked, that many variations occur with regard to these points, 

 and Eschricht's figures represent only some of them. 



§ 55. 

 External peculiai'ities and chemical composition of the Hairs. 

 In embryos, the hairs are generally quite colourless and clear ; 



