306 DR WALTER KIDD. 



direction, which is constant for each region, the only exception 

 to this being the eyelashes. 



Eschricht gives some rather crude suggestions as to the reasons 

 for the various directions found, depending upon the distribu- 

 tion of the vascular system ; but this attempt he did not carry 

 far, on account of the want of correspondence of the branching 

 of the vascular system with the direction of the hair. He also 

 speaks of the attractions and repulsions at certain points to 

 which the ends of the hairs incline, saying that the lines of 

 attraction are the prominences of the surface, especially where 

 the skeleton stands out more sharply, so that the skin is more 

 hardly pressed. But his attempts at explanation are not im- 

 portant, though the descriptions are clear and good. 



Voigt undertakes a more elaborate attempt to account for the 

 variations and peculiarities found on the body. Without going 

 minutely into his theories, it is enough to say that he makes the 

 "diverging whorls," "converging lines," and "boundary lines," 

 for which he supplies definitions, to depend upon a necessary 

 and mechanical cause — viz., the gradual enlargement in three 

 dimensions — length, breadth, and thickness — of the developing 

 embryo. He says the lines of direction of growth of the embryo 

 are not straight, but bent and sinuous, because they are the 

 result of a very complicated growth in length, breadth, and 

 depth of the soft parts just beneath the skin, also of the bones. 

 The growth of the skin itself also has to be taken into account, 

 as it forms over the hollowed, rounded, and bent surfaces of the 

 body, and is thus stretched in the course of growth. He says 

 also that it is clear that the portion of the rudimentary hair 

 within the follicle will be drawn by the gradual stretching of 

 skin in a sloping direction, and the portion external to the 

 follicle will follow this direction. A view of this kind renders 

 the hair-slope a necessary character peculiar to the human 

 embryo, and one dependent on the course which the enlarge- 

 ment of its various parts takes in early intra-uterine life. He 

 also shows' that on certain regions the rate of stretching due to 

 more rapid enlargement is relatively quick, and on others, e.g., 

 the axillary and inguinal regions, where the growth is quiet, 

 the stretching is slow. He describes all the regions of the sur- 

 face of the human body where hair is found, and the theory is 



