INTEGUMENTS. 



End foften, or conftringe and brace ; but no prccifc meaning 

 is attached to thefc vague cxprcffions. They fcem to affect 

 the vital powers of the part, to augment or diminiflj them, 

 but wo know of no influence on the tifluc. 



After macerating the (kin for fome hours in water, with 

 agitation and preiTure, evaporation of the fluid yields a little 

 gelatine. When macerated longer it becomes foftcned, and 

 lenfibly whiter, fwells a little, and remains for a long time 

 without undergoing any other alteration than a degree of 

 putrefaction, much lefs than xvhat occurs in the mufcular, 

 glandular, and other tifTues. This putrefaftion is more 

 marked on the furface in contad with the cuticle, but at 

 the end of two months the flcin has loft but little of its con- 

 fiftence ; it begins to be reduced into a fetid pulp at the end 

 of three or four months. According to Fourcroy, fpon- 

 taneous decompofition in water or ni )ill earth converts it 

 into a fatty matter, and into ammonia, which compofea kind 

 of foap. It produces very little froth when boiled. Juft 

 before ebullition commences, fo as always to be convex on 

 the fide covered by the epidermis, and concave on the oppo- 

 fite ; the fibres are contradled and condenfed at this time, 

 and the contraflion is greater on the inner furface. where 

 tlie intervals are the largeft. At the fame period fmall vefi- 

 cations are obferved. 'This crifpation of the Ikin rendc?rs 

 it denfe, hard, and elallic, but reduces its dimenfions. It 

 foon acquires a femi-tranfp3rency and yellowi(h colour, like 

 that of the fibrous organs when boiled. The hardnefs wliich 

 it had acquired at the indant of crilpation is now gradually 

 loll ; the Ikin is foftened, yields much gelatine to the water 

 in which it is boiled, but inllead of diminifhing, is rather 

 increafed in thicknefs. All appearance of fibres is loft ia 

 this ftage ; a fenii-tranfparent, gelatinous, and homogeneous 

 mafs remains ; ftill it dues not lofe its elailicity ; probably 

 the large quantity of gelatine, which it contains, occafions 

 it to retain this property. The flighteft motion excites in 

 it a general vibration as in the different animal jellies. By a 

 continuance of the boiling nearly the whole gehitine is dif- 

 folved, conftituting a vifcid liquor, which by proper evapo- 

 ration is converted into glue ; and a fmall membranous refi- 

 due only, which is dilfolved with great difficulty, remains ; 

 a long time is required to reduce the fkin to this l!ate. From 

 this (olubility in water, the cutis of animals is moftly em- 

 ployed in the manufaclure of glue. 



Sulphuric, nitric, and muriatic acids aft on the fkin, as on 

 any other animal fubftances, but much more flowly, parti- 

 cularly on the furface coveivd by the epidermis. The firft 

 redixes it quickly to a blackilh pulp ; the two others, even 

 in a concentrated tlate, bring it lefs readily into a pulp : the 

 oxymuriatic acid produces very little effeft on it. Nitric 

 acid converts it into oxahc acid and fat, while, at the fame 

 time, azotic gas and pruffic acid are emitted. Acids do not 

 && in this way during life ; they never produce this pulpy 

 ftate of the organ. A piece of caullic, enveloped in a por- 

 tion of ikin, is reduced to a ye'lowi(h-red thick fluid in the 

 courfe of a day : the fkin is crifped and contrafted, but not 

 penetrated ; its tifiue docs not even appear injured on the 

 furface. Alkalies have different effects, according to cir- 

 cumftances, in the living ftate ; they deftroy fome grnnula- 

 tions much more readily than others. An a kaline hxivium, 

 applied to the furface jf the body, caufes an unCtuous and 

 llippery feel, as its combination with the undluous matter 

 produces a foap. Concentrated alkalies diliolve the dead fkin, 

 converting it into oil and ammonia. 



" The cutis," fays Dr. Thonifon, " appears to be a pe- 

 cuhar moditication of gelatine enabled to refill the aiStion of 

 water, partly by the compaftiiels of its texture, and partly 

 by the vifcidity of the gelatine, of which it is formed ; for 



thofe fkins which diffolve the mod readily in boiling water, 

 afford the worft glue. Mr Hatchett lias obferved that the 

 vifcidity of the ge'atine obtained from (kins is nearly in- 

 verfcly as their flexibility, the fuppleft hides always yielding 

 the weakell glue ; but this glue is very foon obtained frutn 

 them by hot water." Syftem of Chemillry, v. 5. p. 57^. 



The production of leather, by the adion of tlie taiinmg 

 principle of vegetables upon the ikin, is a iubjeft of fi:ch 

 importance, that it would be ufelefs for ns to enter on it here : 

 it will be confidered feparately in the articles of the dic- 

 tionary relating to tanning : further information on the 

 chemical properties of the (kin may alfo be derived under 

 the heads Gklatix, Gluk, &c. 



Very little is known of the chemical conftitution of the 

 rete mucofum. Oxymuriatic acid deprives it of the black 

 colour, and renders it yellow in the negro. Beddoes ftates 

 that immerfion for fome time in water, impregnated with 

 that acid, will difcharge the colour in the living fubjctt. 

 (On Faclitious Airs, p. 4,.) Fourcroy mentior.s that the 

 tooc of a negro, after a fimilar expofure, nearly loft its co- 

 lour, but that the original black hue returned in » few days. 

 Syft des Connoifl" Chimiques, t ix p. 2^9. 



Common Parts belonging to the Tijfue of the Dermoid Syjlem. — 

 The (kin contains a "large proportion of cellular fubftance. 

 Numerous prolongations of the fubcutaneous celiular ftratum 

 penetrate the contiguous areola: of the corion, then pafs 

 into the more exterior ones, and end at the numerous pores 

 which tranfmit the veftels, nerves, and hairs. Thus, if the 

 cellular tiffue could be completely fcparated, the cutaneous 

 organ would reprefent a piece of fponge, being perforated in 

 every direftion. According to Bichat, boils perform this 

 difleClion, deftroy the cellular organ, and leave the (kin in 

 this cribriform ftate. He add^, that the corion itielf is not 

 tlie feat of any acute affedion : that all difeafes of this nature 

 either aff'eCl its furface, or the cellular tiftTue of its areola. 

 But it may be altered by chronic difeafes ; and is mani- 

 felUy diforganized in e ephantiafis. 



In anafarca of long continuance the fubcutaneous ferofity 

 gradually penetrates the cellul.ir fubftance of the dermoid 

 areoix, feparates its fibres, and fometimes arrives even at 

 tlie epidermis, which it burfts ; tlirough thele openings it 

 efcapes. 



Pnibably, fays Bichat, the cellular tilTue does not ex'end 

 fo far as the external furface, under the epidermis : for when 

 that covering is removed, no granu!at:ons are formed, al- 

 though thefe are always produced whenever cellular tilTue 

 isexpofed. 



The arteries, running in tlie fubcutaneous cellular fubftance, 

 furnifti an infinite number of fmall branches, \\hich enter 

 the areolse of the flciii with the cellular prolongations, anaf- 

 tomofe at every point in the areola of the organ, and pene- 

 trate at laft through the pores of the exernaj lurface to pro- 

 duce the capillary net-work already defcribed, which, in the 

 ordinary (late, contains very little red blood. In this paf- 

 fage, through the areolse of the fltin, very few branches feem 

 to terminate on the fibres of the corioii itielf. 



After penetrating the (kin in the oppofite direction, the 

 veins opens into the Urge fubcutaneous trunks, which in 

 many pans may be fo clearly feen through the integuments. 

 The venoUj ramifications of the areola: are nearly lofenfible 

 in the natural ftate, but are onhdjrably dilated over can- 

 cerous tumours, !"o that the (kin is marked by numerous 

 blueifh fcrpeiitiiie lines. All gradual extenfions of the cuta- 

 neous organ, as in aneurifms, pregnancy, dropfy, &c are 

 attended %vith the fame phenomenon, which is never exhibited 

 in acute cafes. 



Nu.merous and confidcrable branches of nerves form a kind 



