INTEGUMENTS. 



^. On the back of the lianJ and foot, as well as on the fore- 

 }icad, the corion does not exhibit thele numerous openings 

 on its inner furfnce ; it is finooth and whitifh, particularly 

 after being mac -rated a little : the fame obfcrvation may be 

 inade concernin- that of the fcrotum, prepuce, and labia. 

 Its tifTue is mor? compaft, and exhibits no intervals ; fo 

 that although it is thinner than on the limbs and trunk, it 

 contains nearly as much fubdance. In that, which corre- 

 fponds to the hair and beard, we obferve only the openings 

 ntceflary for the tranfmiffion of thofe parts. 



The three great modihcations in the organization of the 

 fkin, which we have jull defcribed, are merely differences 

 of form, and not in the efTential nature of the organ. The 

 arcolx may be feen in all parts, where tliey exift at all, by 

 means of maceration, which is a very good method of ex- 

 amining the ftruclure of the /kin. Immerfioii in water 

 foftena the fkin by feparating the fibres of its curion, and 

 rendering their intervals more dillin4t : we then find that 

 the areolx are not confined to the internal furface, but 

 are prolonged inlo its fubllance, which is penetrated by 

 tliem in its whole thicknefs. Thcfe arcolx do not termi- 

 nate in cul-de-faci towards the external furface, but they 

 open on that furface by numerous holes very apparent 

 in Ikin, which has been macerated for a month or two. The 

 epidermis mull be removed in order to render them fen- 

 fible : they penetrate the Ikin obliquely, and admit in fome 

 parts and fome iubjefls tlie introduiition of a pin's head. 

 They are fimple communications from the interior to the 

 exterior for the paffage of hairs, exhalants, and abforbents, 

 as they come to the furface : thus the fubjacent areolae 

 are merely cells containing the blood-veffels, and the tifTue 

 of the fkin altogether is a true cellular net-work, of which 

 the intcrllites are very dilliiift on the infide, but lefs ob- 

 vious externally. Thus the corion conflitutes the balls 

 or ikeleton of the cutaneous organ, lodging in its areolae all 

 the other parts of the organ, and giving to them their 

 proper form. 



Bichat confidcrs that the areolar tifTue, which compofes 

 the corion of the flcin, has much analogy with that of the 

 fibrous fyftem. Its deiifity and refillance are nearly the 

 fame in the heel : it becomes yellowifli and tranfparent by 

 boiling; it refills maceration for a long time; and it re- 

 ceives in fome fituations the infertion of muftular fibres. 

 Yet the fenfibihty and the difeafes of the two fyllcms differ 

 altogether. 



The acute fenfibihty of this organ does not refide in the 

 areolar tifTue of its inner furtaee, but in the part containing 

 the papill.e. And we find that the fame part is the l.-at of 

 mull cutaneous eruptions. The external furface oi)l\ is co- 

 k)ured by the blood in eryfipelas; and hence flight pjeiTure, 

 by driving this fluid into the deeper vefTels, removes the red 

 colour. In meafles, fcarlet-fever, &c. the rednefs is alfo 

 fuperficial. Injcftions occanon much greater rednefs of the 

 external than of tiie internal furface ; as the arterial trunks 

 are found in the latter, and the numerous exhalants in the 

 former. Thefe conllderations prove clearly that tlie cellular 

 tiffiie of the Hcin has much lefs vital aftivity than its outer 

 furface; that this tifTue is foreign to almoll all the great 

 phenomena occurring in the fkin, particularly thofe of fcn- 

 fation and circulation, which take place in the papillx and 

 ' the reticular body. Its funflions, like thofe of the fibrous 

 fyftem, fuppofe it almod always in a pafTivc flat;-, as they 

 coiifill merely in Ihielding the body, and protecting it againlt 

 externa! agentfi. Its properties are well fuited to this office 

 of a general protecting medium. Very large weights are 

 fupporlcd by ik-nder llrips of f^;in, and dragging i . any di- 

 rection tears them with great difScultv. Yet this refillance 

 Vol. XIX. 



is flill much lefs ttian when the corion has been fubmiftod to 

 the aAion of the tunning principle. After fuch preparation 

 it offers the ftrongell conncfting medium which we have in 

 the arts : no other tilfue in the animal economy, except llie 

 fibrous, iinitcs in fo remarkable a degree pliability and re- 

 fillance. 



Haller, wlio ivgardcd cellular fubllance as the principal 

 component part of moll organs of the human body, and 

 particularly as forming the bafis of membranes, defcribes 

 the cutis as being made up of this tiffue in a condenfed form. 

 " Its llruclure," fays he, " is on the whole the Ctiinc as that 

 of membranes ; viz. made of Ihnrt, intricate, and clofely- 

 adhering threads and laininse. Its external furface is denfe; 

 the internal is gradually refolved into the cellular texture, fo 

 that there are no accurate limits between the two parts. 

 Under maceration it fwells and becomes loofcned, and fepa- 

 rates into its component lamince and fibre?, both in man and 

 animals." Elements Phyfiulog, t. v. p. 5. 



The retr muc Jin, or reticular body of the fltin, is fo called 

 from its iuppoied perforations by the papilla: and the hairs, 

 and becaul'e it appears of a foft mucous nature. It was firil 

 noticed by Maipighi, after whom it is fometimes named rete 

 Malpighii. The colour of the furface of the body feems to 

 refide entirely in this membrane : Riolan faid that the caufe 

 of the black colour in the negi o is in the epidermis, and does 

 not go fo deep as the true fkin. Maipighi, by fhewing the 

 dilliiiAion between the cuticle and rete mucofum, demon- 

 llrated the true feat of the colour of the body. " Ex quo," 

 fays he, " deduce non incongruam forte nigredinis .£;hio- 

 pum caufam: certum enim eft ipfis cutam albam elTe ficuti et 

 cuticulam, unde tota nigredo a fubjedo mucolo et reticu- 

 lari corpore ortum trahit." 



The rete mucofum in the negro is a thin black layer, 

 about as thick as the cuticle itfL-lf. Putrefaction eafily de- 

 taches it with the cuticle from the cutis ; but it can liardly 

 be feparated from the former. It diflolves in water, and 

 communicates a turbid cloud to it, like that produced by 

 the pigmentum nigrum. Mr. Cruikfhaiik defcribes it as 

 being " double, and confilling of a grey tranfparent mem- 

 brane, and of a black web, very much refcn;bliiig the nigrum 

 pigmentum of the eye." The demonflration of this reti- 

 cular body is much lefs eai'y in the white races than in the 

 negro ; and indeed very little feems to be known concerning 

 its anatomy in the former. " Moll authors," fays Bichat, 

 " reprefeiu the i-ete mucofum as a m\:cous ftratum interpofed 

 betvxeen the cutis and epidermis, and pierced by a large 

 uumber of openings for the paffage of papillae ; but I do 

 not underlland how this can be demonftrated on detaching 

 the cuticle, if it be fluid according to the ufual defcription. 

 I have employed, for difcovering it, fevcral means, none of 

 which has fucceeded. So clofcly does the cuticle adhere to 

 the cutis, that they cannot be feparated without injuring one 

 or the other in the recent fiate. Yet, if we fucceed in au 

 attempt of this kind, there is no appearance of mucus on the 

 corion. After a longitudiniU ft Ction, particularly in the foot, 

 where the cpiiderinis is very thick, the line of diftinftion be- 

 tween it and the corion is very manifoft : but nothing efcapes 

 from between them. When the cuticle has been removed, 

 after lioiling the fkin, nothing remains on either of the fur. 

 faces. Maceration and putrcfa£tion, but particularly the 

 latter, produce a kind of vifcid covering on the fkin, very 

 obvious when the ejiidermis is detached: but this is pro- 

 duced by decompofition, ;;nd nothing of the kind is leen 

 uader ordinary circumllanccs. I believe, from all thefe con- 

 fiderations, that there is no fubftance depofited by the vcf- 

 fels on the furface of the cutis, and forming an exterior co- 

 verinjf in t!ie icnfe is v hiv,h .Maipighi has reprofented tho 

 V i matter. 



