CHAPTER VII. 



THE EVOLUTION OF PATTERNS OF HAIR. 



Some attention must here be given to the supposed mode of forma- 

 tion of individual patterns of hair, that is to say, their evolution. 

 So here one has to move among the fields of hypothesis, without 

 which detached facts of nature are useless to science. 



The simplest pattern consists of a reversed area of hair 

 appearing between two adjoining streams ; the more complex 

 are whorls, featherings and crests. No detailed description nor 

 illustration of the former are required, but I have prepared a 

 diagram to illustrate the latter (see p. 51.) (a) shows a whorl by 

 itself ; (b) a whorl, feathering and crest. The arrows at the sides 

 indicate the direction of the adjoining hair-streams, the arrow in 

 the centre of (b) the direction of the reversed flow of hair. 



An understanding of the dynamics of a hair-whorl leads quite 

 simply to that of a feathering and crest, for the two latter are 

 only the results of the further extension of the battle of forces 

 concerned in the whorl itself, and the end of their conflict. A 

 whorl marks a point in the stream of hair where two contending 

 forces have come into collision ; on the one hand the centrifugal 

 force of growth from each hair-papilla, the rate of which has been 

 described, and on the other a certain centripetal dynamic force 

 which may be either that of localised friction, pressure, gravitation, or 

 muscular traction, directly opposing or divergent. Thus conceived 

 a whorl may be looked at symbolically as a written treaty between 

 two nations, one of which has defeated the other, and actually as 

 a proof that the contending centrifugal and centripetal forces are 

 in the state called the balance of power. But when the centripetal 

 force of some habitual action prevails over that of the original 

 force of growth in the hair, a whorl becomes extended into a 

 feathering, and the length of this, metaphorically speaking, 

 corresponds with the duration of open fighting, and terminated by 

 a sharp crest when another and a decisive battle has been fought. 

 A crest may again be looked upon as a " treaty." The whole 

 process pictured here shows a battle followed by a treaty or truce 

 (w) again a retreat (f) and a counter-attack (c) with a final treaty 

 and peace. 



