INTEGUMENTS. 



ticaUrly the blood-vcnels, to be eafily feen through it. 

 Its coniiRi'iice incrcafes until it acquires the appearance 

 exhibited at the time of birth. In its mucous ftate cel- 

 lular fubftnnce and veflels compofe it entirely : when the 

 fibres of the corion are added, it becomes firmer. The ex- 

 ternal - furface exhibits but few of the wrinkles defcribed 

 above: they are" prevented from appearing by the large 

 quantity of fubjaccnt fat. The inner furface adheres but 

 flightly to, the cellu'ar layer under it. It contains more 

 blood than at any other period of life. The animal fenfi- 

 bility is not yet called into e.\ercife ; there are no caufes to 

 excite it. " Is the organic feiifibility in aftion at this time ? 

 It muH: be fo in a certain degree to produce the unftuous 

 fecretion, by which the furface is covered. 



This fyftem undergoes a fudden revolution at the in- 

 ftant of birth. Hitherto it has received only black blood, 

 and is confeqnently more or lefs livid at birth. This colour 

 pvcs place to red, produced by the arterial blood now firft 

 formed : and the ftate of the flcin in this refpecl may be 

 confidered as an index of what is pafiing in the lungs. Ail 

 parts of the organ are penetr.-\ted uniformly by the red 

 colour. A fudden excitation is thus communicated to the 

 organ, exalting its vital properties, and rendering it more 

 fufceptible of the impreflions of furrounding objetts. Tlie 

 furrounding temperature, the air, clothe-s the water ufed 

 in wafhing it, communicate to the lldn an excitation, which 

 is the more lenfible in proportion to its novelty. Tlie 

 fympathies conneamg the fkin to the other organs now 

 become neceffary : tluis the internal organs quickly feel 

 the excitations applied externally. 



The organic fenfibility is augmented at the fame time ; 

 tranfpiration is ellabhfhed ; varions (ubllances are feparated 

 by it ; others perhaps abforbed ; and various difeafed af- 

 feftions fhew th.emfelves. 



The organ ilill continues foft for fome time after birth ; 

 and melts entirely into jelly very eafily by ebullition. Its 

 -denfity increafes gradually, but has not arrived at its greateft 

 ftate till towards the thirtie h year. As this augmen- 

 tation proceeds, the i'.brous fubllance is increafcd in pro- 

 portion to the gelatinous. At the fame time the adhcfion 

 •of the internal furface to the cellular fubllance becomes 

 ftr 



and the wrinkles of the face are gradually formed. 

 No remarkable change is produced in this organ at puberty : 

 fweats are more ?.bundant after this time ; in children the 

 refidue of nutrition pviffes off by the kidnies rather than 

 by the Ikin. 



The organ ftill retains a great aftivity after the age of 

 growth, and very eafily influences other parts of the frame : 

 hence the peripneumonies, pleurifies, &c. produced by the 

 aftion of coid. 



The increafe of the fibrous fubftance renders it more 

 firm ; lefs blood feems to be fent into its vefiels, and it 

 is kfs fubject to thofe eruptions fo common in infancy and 

 youth. 



In declining age the dermoid fyftem becomes more and 

 ■more denfe : it refills obullition for a long time, but yields 

 a firmer and more confiflent, though lefs abundant jelly. 

 It is (Ironger but lefs phant. The blood penetrates "it in 

 fmaller and fnialler quantity : the rednefs of the cheeks 

 difappears. The adhefion to the cellular fubftance is much 

 more clofe. All the wrinkles are more llrongly marked, 

 and feveral are now perceptible for the firft time. 



The vital poiver-s of t!>e ll^in are more weakened than 

 ihofe of other fyftems in the old man, becaufe it has been 

 more excited by external objeiStB during life : the habit of 

 fetling has blunted its ierifibility. The touch is now exer- 



cifed but rarely ; as this fenfe is employed in a great meafure 

 in fubferviencc to tliofe of fight, hearing, &c. to rcftify or 

 confirm our other fcnfations, the old man, being acquainted 

 with what furrounds him, has no motive for the ufe of his 

 organ of touch. Contraft, in this point of view, the two 

 extremes of life. The infant, to whom every inipreflion on 

 the fight, hearing. Sec. is new, wifties to touch, to feize 

 efery thing : his hands are in conftant motion. Touching 

 is a great plcafure to him, becaufe all new fenfations are 

 agreeable. If an old man were placed in the midft of ob- 

 jeds, which had never before imprelled his fenfes, he would 

 exercife his touch more frequently ; but, among the things 

 to which he is habituated, there is n<jtliing to excite him. 

 Kence old age is no longer the time of enjoyment. Ahnod 

 all our pleafures are relative-; as habit renders thcfe lefs 

 lively, they ccafc in confequence of having exilled ; thus 

 the advance of )ears, by leaving us few new fenfations, 

 dininilhes the fcurces of our happirefs. For the contrary 

 reafon the happitft age is that of infancy ; becaufe the 

 whole dom:'in of fenfation lies tefore us unexplored ; at 

 every ftep of his advancement man leaves behind him a fource 

 of enjoyment. His career ends in indiiferenee, a ftate very 

 fuitable to that period, as it diminilhes the interval between 

 life and death. 



The foil- wing phenomena fliew that the organic, as well 

 as the animal fcnfibihty, is remarkably diminilhed in the 

 old man. Contagions are lefs eafily abforbed. The fneat 

 is lefs abundant, and hardly ever exhibits thofe augmentations 

 which are fo frequent in the adult. The greafy covering 

 i-; lefs copious, and hence the furface is drier. The various 

 morbid ajffeftions, fuch as eryfipelas, and the various erup- 

 tion?, are lets common and much flower. The power of re- 

 fifting cold is fenfibly diminiihed. 



Epidirmoiil or culiciilar S\fiem. — The llighteft examination 

 is fufficient to Ihew very linking differences between this 

 and the preceding fyftem^ although phyfiologifts have ge- 

 nerally defcribed this merely as a dependance of the former. 

 The organization, properties, funftions, mode of ^owth, 

 in flior[, every circumftance is different in the two cafes. 



Under this head we confider the exterior epiderir.is ; that 

 which covers a part of the mucous fyilem ; and the nails. 

 Many charadlers approximate the latter to the epidermis, 

 akh'ough the external appearance is very different. 



Tiie exterior e^icliniiis is a tranfparent layer, differing in 

 thickiiefs in different parts, every where covering tlie (kin, 

 and immediately expofed to the excitation of external 

 bodies. 



It has the fame inequalities as the cutis, fince they are 

 every where exactly contiguous. Various pores penetrate 

 it, and terminate on its furface : the more ccnfpicuous ones 

 tranfmit the hairs ; others give paftage to exhalants. The 

 litter are. not eafily feen ; but if, wiien the fk'n is dry, we 

 fnddenly begin to fweat, we can dillinguiih them by the 

 fmall points of moillure then exhibited over the whole cu- 

 taneous furf ice. We cannot actually fee the pores in the 

 dead cuticle, even with the afTulance of the raicrofcope ; 

 and the fluid under a blifter does not efcape through them : 

 but the phenomena exhibited daring hfe leav» no doubt of 

 their exillence. The internal furface adheres mull clofcly 

 to the omer furface o£ the cutis. We conceive the union 

 to be by means of the exhaling and abforbing vefltls and 

 the hairs. Dr. Hunter tlioughl that the velicls culd be 

 demonftrated. On feparating the cuticle after long ma- 

 ceration, particularly in the fole of the foot, a vaft number 

 of extremely fn.e and foft tiireads are fecu paffing between 

 it and the cutis : they break after being extended to about 



