JiLY, 1902.] 



KNOWLEDGE 



147 



visible iu tlie other three adult specimens. In producing 

 this luuuc'in peculiarity clothing is jirobably the efficient 

 cause. It is easy to see that in respiration, which involves 

 much movement of the upper ribs, a force is actiuj; in 

 inspiration and absent when the chest falls in expiration, 

 calculated to draw the growing stream of hair in this, the 

 line of least resistance. Here is an adequate cause acting 



exactly corresponds to the direction which would be in- 

 duced by the normal attitude of man in sleep, viz., on one 

 or other side and with the head, and perhaps the shoulder, 

 raised on a i>illow. Here, again, as there is a force calcu- 

 lated to produce what we find existing for about a third of 

 a human being's life, it is unnecessary, according to "the 

 law of parsimony," to go beyond such an explanation. 



f^Mr^ ffV^'d , ■^''^^:ii' p 





^7^1 ltt# Sim tk 



i^fh^'fi 



'^\ 



y 



\ 



y^- e^oZdfncL^ <?e7. 



Two views (A ami B) of tlic assumed prototype of Man, showing the jirimitive direction of hair. 



Seven views (CD. E. F. a. H. I) of Man's bo'lv.— Primitive tracts of hair shown by arrows with single heads. 



Those acquired by morphological changes marked by arrows with two heads. 



Those acquired by use and habit marked by arrows with three heads. 



during two-thirds of man's life, i.e., during daytime, when 

 the effects of pressure against clothing would come into 

 play. 



(jii the lower part of the eh'.st and the front (>f the 

 abdomen such changes as are found are probably due only 

 to morphological change. 



The side of the abdomen shows the singular parting-line, 

 figured (Fig. C) as extendinsr from the axilla to the level 

 of the umbilicus, here sometimes terminating in a whorl 

 and. in most cases, extending to the groin. Tiiis wholly 

 human peculiarity is most probably accounted for by the 

 fact that in sleep on one or other side, which is the greatly 

 predominant attitude, the arm lies along this parting and 

 determines the separation of the alidominal and dorsal 

 streams in accordance with the principle that these flow in 

 liie lines of least resistance. 



On the haek the direction of hair in man and his ]iro. 

 totype are markedly contraetcd. . The upward Klnp., nhnwn 



The equally strange slope of hair which is seen at the back 

 of the arm"-]>it is also directed iu a way which this force 

 referred to would produce. In addition to the mechanics 

 of the position during sleep, the mechanical eii'ect of sitting 

 with the back leaning against any supjKirt emphasizes the 

 existing direction on the shoulders and upper part of the 

 back. Our Troglodyte ancestors cannot well have been 

 luxurious persons, but even they must have had many 

 liours of their strenuous lives free enough to lean against 

 the trunk of a tree, the side of a cave, or some bank of 

 earth, and when we come to the case of modern man, the 

 opportunities tor such indulgence have been obviously 

 much increased. 



On the upper extremitij the complicated slope of hair 

 strikes one on looking at Figs. C, D. On the upper half 

 and outer side the singular upward direction which begins 

 ut the insertion of the deltoid is clearly of the same 

 nature Rnd duo to the »ftmo GftUBivtion ivs the pefiuliaritifs 



