THE SKIN AND HAIK. 71 



and the same species, and one and the same part of growth, 

 there may be much variety as to the fineness of hair, as the 

 human head exemplifies. As to the further structure of hairs, 

 it is more complex than those people may imagine who abuse 

 it by hair-dye so remorselessly. The stem of each hair is 

 covered with a coating of scales overlapping each other like 

 those on the skin of a fish. Hence comes the property of felt- 

 ing, which only consists in beating a layer of hairs, laid upon 

 a flat surface, sharply until they interlace and hold tight one to 

 the other, held by their rough external surfaces. Inside this 

 scaly covering comes a fibrous substance, making up the chief 

 part of the stem ; and in the very middle of it, running like a 

 streak of alder-pith along a branch, is often a sort of marrow. 

 This central pith, however, does not exist in all hairs. It is 

 wanting in the fine hairs over the general surface of the body, 

 and is not commonly met with in those of the head. The 

 special pigment that constitutes the difference of colour be- 

 tween different hairs resides in this pith when present, also in 

 the fibrous matter. 



We now come to the hair-root. It is lighter in colour 

 and softer than the stem, swelling out at its lower end into 

 a bulbous knot, lying in a special recess called the hair-fol- 

 licle, which may reach down to the subadjacent fat. It is 

 known that women more rarely grow bald than men, and 

 it is accounted for by the circumstance that women have 

 more fat underneath their head-skin, thus furnishing a richer 

 soil, so to speak, for the feminine tresses to spring from. 



Usually hair is wholly devoid of sensation, else it would 

 go hard with us when we submit to hair-cutting. There is a 

 certain disease, however, not unusual in Poland, and known 

 as the plica polonica, the characteristic of which is that the 

 hair grows sensitive, and when cut bleeds even dangerously. 

 Some physiologists have entertained the belief, that from the 

 insertion of each hair-filament to its extremity a fluid passes, 

 and thence back again. The reality of this circulation, how- 



