224 



NA TURE 



[July 7, 1904 



surface of the liquid in the trough below. He also remarks 

 that a machine could be devised which would pump up the 

 liquid and open the stop-cocks at the proper times, and 

 thus make the action continuous. 



The paper is illustrated. 



July I. Herbert McLeod. 



RATS AND HAIR. 



PUBLIC attention has been recently directed to the 

 head-gear of civilised man, which, it is held, is 

 neither necessary nor advantageous. We have here 

 one of the attempts of well-meaning reformers to regu- 

 late on rational principles the dress of man, and so to 

 assist him in his work of self-adaptation to his sur- 

 roundings and needs. The object is laudable, and in 

 all probability the scientific truth is with the reformers, 

 but it may be well to review the question on somewhat 

 broad lines. 



The scalp is unique among the areas of the human 

 body where hair is abundant, for there has been a 

 notable development of hair in both sexes in this 

 region beyond what can have existed in any of the 

 Anthropoidea that can be placed in the human family 

 tree. This is the more remarkable because man's 

 pelage is a degenerating and disappearing character, 

 except in a few areas. We must assume that when 

 primitive man was in the making, natural selection 

 led to the growth of thick hairy covering on his head 

 which conduced to success in the struggle of life by 

 protection against excessive heat and cold, against 

 rain, and against minor injuries. As he advanced 

 from his ancestral arboreal home into the open, and 

 the range of his life extended, -such natural adverse 

 influences as these would call forth useful adaptive 

 modifications, such as increased thickness and length 

 of hair. At a later stage his developing intelligence 

 would bring the same character under the influence 

 of sexual or physiological selection, and this would 

 strongly supplement the earlier factor of natural selec- 

 tion. Between these two factors a very stable char- 

 acter of the race has been produced. 



There is considerable evidence that in spite of the 

 stability of this character, the vigour of the hair on 

 the head of man, especially in the male sex, is de- 

 clining. The complexity of the conditions of civilised 

 life renders it impossible to prove that this is due to 

 the cessation of natural selection and the inability of 

 sexual selection to arrest decline, but it is highly 

 probable that this is the case. The more immediate 

 question is this — is a decline in the growth of hair 

 part of a general degeneration of man's ancestral 

 pelag-e, or is it due to some factor introduced by man 

 himself? It is declared by the reformers that the 

 wearing of head-gear is responsible for the increase 

 of premature baldness. Hitherto the discussion of 

 the question has consisted of little inore than indi- 

 vidual opinions and ex-parte statements, and it is 

 doubtful if evidence can prove or disprove the doctrine 

 now being advanced. Experiment is, from the nature 

 of the case, out of the question, because of the length 

 of time required and the general complexity of the 

 problem. It would seem that the nearest approach 

 to a solution must rest on analogies derived from 

 other characters of man himself and from the lower 

 animals. The study of adaptive modifications (the 

 " modifications " of Lloyd-Morgan and the " onto- 

 genic variations " of Osborn) shows that they thrive 

 when exposed to the natural conditions amongst which 

 they arose, so long as these do not become excessive. 



The wearing of coverings for the head affects the 



hair which is covered in three ways — the natural 



forces of sunlight, free ventilation, "and movement 



from wind are prevented, the arteries which supply 



NO. 18 10, VOL. 70] 



the skin of the scalp and nourish the hair-follicles are 

 compressed, and nutrition thereby diminished, and 

 the head-dress affords a culture-ground for micro- 

 organisms, being also itself impregnated with them. 

 The absence for the time being of the germicidal effect 

 of the sun's rays and of movement of air, and the 

 warmth and moisture of the contained air are just 

 those conditions which would be chosen for the 

 culture of these low vegetable organisms. Very much 

 of the premature baldness of men is due to dandriff 

 {Scborrhoea sicca capillitii), a disorder of the sebaceous 

 glands characterised by excessive secretion of sebum 

 and its accumulation in crusts with an admixture of 

 epithelial debris, which leads to destruction of the 

 hair-bulbs, and this disease is essentially microbic in 

 origin. Froin these various points of view it seems 

 to be indicated that the wearing of coverings for the 

 head slowly diminishes the vigour of the hair. If this 

 theoretical side of the matter cannot be demonstrated, 

 but is only extremely probable, the practical outcome 

 of it is no less beset with difficulties. A change of 

 custom, if desirable at all, is less called for in the 

 case of women than of men, for in the former the 

 head-gear is mostly of light texture and covers a very 

 small portion of the vertex, at any rate in modem 

 times, and a much larger surface is left exposed to 

 sunlight and air than in the case of men. In addition 

 to this fact it is to be remembered that the evidence 

 for decline in the growth of hair is much less in 

 women than in men. Those whom the practical 

 matter chiefly concerns are children of both sexes, 

 young adults, and all male adults, and to these the 

 reformers speak from a sound physiological basis. 

 Whether or not their advice will be taken, or ignored 

 as a counsel of perfection, remains to be seen, and 

 the change advocated is certain to be the occasion of 

 extravagant partisanship. 



Certain objections to it may be anticipated and re- 

 moved. First, it will be declared to produce " colds." 

 It is most unfortunate that this name is given to what 

 modern medicine calls "catarrh." The belief that 

 " colds " are produced by exposure to draughts or 

 cold winds is dying hard, and is fortified by the old 

 name so long applied to them, but it is to stultify 

 the great teachings of bacteriology to invoke some 

 casual draught as the cause of disorders of which a 

 nasal catarrh is a type. This danger may be entirely 

 disregarded. It would indeed be for the benefit of 

 the public in more ways than one if they became 

 imbued with the knowledge that pathogenic bacteria 

 of some undetermined species are the eflicient cause 

 of all catarrhs. Secondly, it may be feared that in- 

 flammatory complaints, such as neuritis or " rheu- 

 matism " in the head, would arise from uncovering the 

 head. This is highly improbable considering how 

 large a surface of the head is always uncovered, and 

 that there is no greater protection from hair in the 

 parts uncovered than there is on the vertex. Thirdly, 

 there is undoubtedly some danger, even in temperate 

 climates, from exposure of the head to great sun-heat, 

 and against this danger special precautions are and 

 always would be taken. Fourthly, there is the danger 

 from septic organic matter in towns. This can hardly 

 be reckoned as important, for the area which is neces- 

 sarily exposed to it is considerable, and proper hygiene 

 of the hair would render it unimportant. Fifthly, 

 injury to the texture of the hair from heat and cold 

 winds is feared, and this again is negligible in view 

 of the fact that the already uncovered parts of the 

 head are better provided with vigorous hair than the 

 covered parts. 



Whether the reformers have scientific truth on their 

 side or not, it is possible that the assthetic aspect of 

 the matter will prove the stronger. 



