INTEGUMENTS. 



f>f the figure : \re attach the ideas of majefty and grandeur 

 lefs to the brcadtli of the forehead, than to its perpendicular 

 direflion. The number of the hairs in a given furfacc is 

 fingularly variable : they may be fo clofe as to touch in every 

 point, or may leave intervals in which the (Icin of the cra- 

 nium is vifible. We hardly know the natural extent of 

 their growth. They will fometimes become fo long as to 

 touch the thighs or even legs ; and this circumftance, like a 

 crowd of others, tends to prove the deftination of the hu- 

 man fubjet\ to the ereft attitude. It has been quellioned 

 whether the praftice of cutting them produces any phy- 

 fiolo^cal cfFcift ; whether the conllant growth, rendered 

 ueceffary by this praftice, be performed at the expence of 

 any other parts or funfiions. 



The ftrength of the hair is very confiderable in propor- 

 to its flender bulk : no part in the animal economy, not 

 even the fibrous fyfteni, will fupport ftich confiderable 

 weights. Ropes made of hair would therefore be very ufe- 

 ful, if they could be procured of fiifficient length. 



Smooth and ilraight liair grows to the grcateft length ; 

 in proportion as it is curly it is fhorter, of which the woolly 

 kind in the negro is a remarkable example. . The colour 

 varies in the different races of mankind, and thus becomes a 

 cliaraftcriftic attribute in the natural hiilorj- of the fpecies. 

 But it varies no Icfs in the different individuals of the fame 

 fpecies ; and thefe varieties follow the fame general rule 

 with that which regulates the colour of the ficin and eyes. 

 Hence thefe differences are to be confidered in enumerating 

 the charafters of the different temperaments. 



The eyebrows and eyelatlies are defcribed under the ar- 

 ticle Eve. The hair compofing the beard, which we have 

 alluded to in the article Gener.'VTIox, as one of the fexual 

 diftinftions of the male, is ftiorter than the covering of the 

 head, and longer than any other hairs in the body : it is 

 always more or lefs difpofed to curl, is itronger and lefs 

 greaiy than the hairs of the head. It generally follows 

 their colour ; but very often deviates into the red tint. Its 

 quantity varies fingularly in different individuals : common 

 opinion affociates the idea of ftrength to its abimdance, par- 

 ticularly if it be black. For fome remarks on the effedls of 

 cutting it, fee Hair. 



2. Hairs cf the Trunk — Their quantity is expofed to 

 »ery great variations ; fome being almoli covered, while 

 Others have the furface perfectly fmooth. Tiiey are much 

 more numerous in front than behind : and in the former 

 fituation abound chiefly on the chell, and in the courfe of 

 the linea alba in men. There are none on the thorax in 

 women, who have altogether but few on the trunk. A 

 confiderable collection, refeu|bling the beard in its nature, 

 is found about the generative organs in both fexes. Thefe 

 are very feldom light in colour, frequently approaching to 

 red, and very commonly black. This increafe of the hairy 

 fyftem is almoft peculiar to the human fubjeft. Its quan- 

 tity varies very greatly. 



3. Hairs of tin Extremities. — Thefe organs are for the 

 moil part covered : the number of their hairs is nearly uni- 

 form in moll individuals, but the lergth differs greatly. In 

 the hollow of the axilla, a fuiall coUedion occurs refembliug 

 thofe of the genital organs : but there is nothing like this 

 in the lower limbs. Tiic inner furface of the arm and fore- 

 arm has none of this covering in moil men : but the lower 

 limbs are more uniformly covered ; the back of the foot 

 and hand are conllantly covered, but the palms and foles, 

 and coirefponding furfaces of tiie fingers and toes, are al- 

 ways perfeftly fmooth. The latter circumftance feems to 

 contribute to the pcfcdlion of the organ of touch. 



On the organization and mode of growth of the hair, the 

 reader is referred to that article. 



Properties of the Hair. — It experiences but a flight cor- 

 ru'iation from the aiflion of heat, but it is twifted or curled 

 in various dircftions : moifture makes it ftraight again. It 

 hardly poflVnes any extenfibility or contractility. Whether 

 they have any vital properties is a fubjecl of difpute : at all 

 events they are exceedingly obfcurc. We are difpofed to 

 deny their exiftence in this fyftem, as well as in the epi- 

 dermis and nails. Bichat, who, for fome of the reafons 

 explained in the article H.^iu, conceives that they are the 

 feat of vital proccfTes, adds, " we cannot however deny, that 

 in ib.e natural ftate thefe organs come next to the epidermis 

 and nails in poffeffing the Icall active life, and having the 

 feweft relations to other organs. While all other fyllcms 

 are deranged by difeafe, this is generally unafftclcd ; the 

 hair grows as ufual, and fecms not to experience the fliglitcll 

 diflurbance ; its mode of exiftence is, therefore, quite dif- 

 ferent from that of other ftruiSlures." 



Mr. Hatchett concludes, from his experiments, that hair 

 contains gelatine, and owes its fupplenefs and toughnefs 

 to that matter. This may be feparated by boiling it iu 

 water, after which it is much more brittle. If the proccfs 

 be continued for a long time, the hair crumbles in pieces 

 between the fingers. The portion infolnble in water pof- 

 feiTes the properties of coagulated albumen. Vauqiielin 

 obtained a folution of human hair in water, by raifing tl^e- 

 temperature of the fluid in Papin's digefter. When the heat 

 was too great, it was decompufed, and ammonia, carbonic 

 acid, and an empyreumatic oil formed. Sulphuretted hydros 

 gen is always evolved, and its quantity increafes with the 

 heat. The folution of liair effeded in this way contains a 

 kind of bituminous oil, which is depofited very flowly. Tlie 

 colour of this oil correfponds with that of the hair. Fil- 

 tration allows a colourlefs fluid, in which copious precipi- 

 tates are formed by infufion of galls and oxymuriatic acid, 

 to pafs through. Silver is blackened by it, and acetate of 

 lead precipitated brown. Though very much concentrated 

 by evaporation, it does not concrete into a jelly. Water, 

 containing four per cent, of potafti, difTolves hair with an 

 evolution of hydrofulphuret of ammonia. A thick oil, dif- 

 fering in colour according to that of the hair, with fome 

 fulphnr and iron, remains undiffolved. Su'phuric, muriatic, 

 and nitric acids dilTolve it : v.ith the latter an oil is fepa- 

 rated. Oxymuriatic whitens, and then reduces it to a fiib- 

 llance of the confiflence of turpentine. Alcohol, digefted 

 on hair, extrads from it two kinds of oil : the firll is white, 

 and fubfides in white fcining fcales as the liquor cools ; the 

 fecond varies according to the hair employed : it is greyifh- 

 green when black hair is ufed, and as red as blood when red 

 is employed. When incinerated it yields iron and nianga- 

 ncfe, phofphate, fulphate and carbonate of hme, muriate of 

 foda, and a confiderable portion of filica. The aflics of red 

 hair contain lefs iron and man^anefe ; thofe of white iiair ftill 

 lefs, but tiiey contain magnefia. The aflies do not exceed 

 0.015 °f the hair. According to the above experiments, 

 performed by Vauquelin, black hair is compofed of the nine 

 following fubftances ; 1, an animal matter, which conftitutii 

 the grcateft part ; 2, a white folid oil, in fn.all quantity ; 

 3, a greyifh-green oil in greater abundance ; 4, iron in an 



iknown ftate; 5, oxyd of manganefe ; 6, phofphate of 



lime ; 7, carbonate of lime, in very fmall quantity ; 8, filica ; 

 chap. 2. fed. 7. 



and 9, fulphur. Thomfon'o Syftem of Chemiftry, book v. 



Developemcnt of the Hair. — In the firft months none can 

 be perceived. When the fibrous part of the cutis begins 



