NOTES ON THE HAIR-SLOPE IN MAN. 

 By Dr Walter Kidd, F.Z.S. 



The following observations were suggested by a study of the 

 singular slope of hair found on the extensor surface of the fore- 

 arm, which has been looked upon by many writers as a vestigial 

 character. In Nature, vol. Iv. p. 236, I wrote a short paper with 

 the purpose of showing that this character in Man is not ves- 

 tigial, and in Natural Science, 1897, p. 357, a short note main- 

 taining that this peculiar direction of hair-slope on this limb- 

 segment, both in Man, Anthropoid Apes, certain Monkeys, and 

 many Carnivores, is due to the effect of use or habit transmitted 

 through numerous generations. It is not necessary here to re- 

 capitulate this argument. Also in last June, at the Zoological 

 Society, I read a paper on the significance of the hair-slope in 

 certain mammals, especially in the frontal and nasal regions, 

 and on the flank and post-humeral and pectoral regions of the 

 Horse. These characters being inherited, the suggestion was 

 that they are due to certain habits and environments of the 

 animals in question, and thus they are the result of Lamarckian 

 factors, and, so far, that a series of instances of inheritance of 

 acquired characters had been adduced, contrary to the well- 

 known doctrine of Weismann. 



The direction taken by the hair covering the human body is 

 a matter already well elucidated by the elaborate descriptions 

 and illustrations of Eschricht in 1837 ^ and by C. A. Voigt in 

 1857,- who both made numerous observations as to the hair 

 on the human foetus. To these I have nothing to add of any 

 importance after numerous examinations of hairy young human 

 subjects and a few foetuses. It appears that on all parts of the 

 human body where it exists, the hair slopes at an acute angle 

 with the plane of the adjoining surface and always in a definite 



^ Archil- fur Anat. undPltys., 1837. 



- Dcnkschrlftenderk. k. AkarJ. zx. Wien, Bd. 1-3, 1857. 



