EVIDENCE FROM ARRANGEMENT OF HAIR 4i 



as specific characters. Various other papers at the Anatomical 

 Society of Great Britain and Ireland were read and published and 

 others at the Zoological Society, in which different regions of the 

 hairy coat of man and lower mammals were dealt with. In 1903 

 the whoJe subject of the Direction of Hair in Animals and Man was 

 treated in a book freely illustrated. 



I then followed the advice of Horace and left the subject alone 

 for nine years, during which time my further observations and 

 reflections served but to confirm, except in two or three unimportant 

 details, the results and conclusions in the book and papers of an 

 earlier date. The connection between the habits of an animal 

 and the distribution of its hairy coat were always cropping up, 

 and I saw then and see now no possible explanation of the con- 

 nection than that the former is the efficient cause of the latter. 



How the Hair is Arranged on the Forearm. 



Returning now to the text, the remarkable arrangement of 

 hair on man's forearm, attention may be directed to the accompany- 

 ing figure of the forearm of a lemur, an ape and man, in which the 

 extensor or back view of this limb-segment is shown, the heavy 

 " war-arrows " being employed to direct the attention of the reader 

 to the main lines in which the hair-streams flow. The front or 

 flexor surfaces in the lemur and ape are not shown because they 

 are precisely like the corresponding back surfaces, and the flexor 

 surface in man is shown in the figure. The figures are so much 

 like diagrams that a 'very little detailed description will suffice. 

 For the examination of the hair on man's forearm the best subject 

 is a dark-haired youth, and it is easily traced, though in any 

 hairy subject it can be shown up well by placing the forearm 

 in water for a minute and allowing the water to drain off. 

 The normal and congenital hair-slope on the forearm is then well 

 displayed. 



On the front surface of man's forearm the hairs point away 

 from the elbow and divide in the middle of the surface into two 

 streams, one pa^sirg to the outer and the other to the inner border 

 in a downward gentle curve, and they join the streams of hair on 

 the back surface. In this pattern there is nothing very peculiar, 

 for it is shared by many monkeys. 



When the back surface is examined it is found to present an 

 arrangement of the hair which is unique among hairy mammals. 

 The figure shows the eccentric course taken by the hair on the 

 back surface. In the centre, exactly along the extensor border of 

 the ulna, from the wrist to the point of the elbow, the hair-stream 



