INTEGUMENT5. 



and warm to the other, if \vc have previoufly immerfed one 

 in a warmer, and the other in a colder medium. 



It has been conceived that the fenfe of touch is of great 

 ufe to us iu^orrefting the errors of the otiier fenfes, and 

 particularly of the fight. This pecidiarity bclnngs to it 

 certainly, that the organ is modified by'the very body whofe 

 properties we are examining ; while, in the cafe of viiion for 

 example, the eye is aifefted not by the objeft itfelf, but by 

 the rays of hght. Perhaps we are lefs deceived by the other 

 fenlcs, and by that of fight itfelf, than has been commonly 

 imagined. Without any afliiiance from the fenfe of touch, 

 for which his organization entirely difqualifies him, the horfe 

 meafurcs the hedge or ditch with his eye mod accurately, ar.d 

 clears the diftance with great exaftnefs. Newly born animals 

 feem to commit no errors in feekiug their food or their 

 parents, &c. On the other hand, the touch is not free from 

 error. The experiment of rolling a round body under two 

 f.ngers decuffated, which give us the fenfation of two bodies, 

 fncws this. Moreover, the touch no more inforjns us of the 

 real nature of things, than any other fenfe ; we acquire a 

 knowledge of their properties through certain interp^ifed 

 media, and alterations in them very much modify the percep- 

 tion. When the epidermis is removed, external bodies caufe 

 pain, and do not excite the imprefiions, which inform us of 

 r jngible properties ; again, when the cuticle is preter- 

 nnturally thick, as in thehanas of labouring men, no fenfa- 

 tion takes place. 



This fenfe is alfo fubjeft to various morbid conditions. In 

 hvpochondriacs there is fometimes a feeling as of cold air ; 

 and the flightcft contaft of air is intolerable. Ann of 

 Auftria found the fmell linen manufaftures unpleafantly 

 rouo-h ; and fome have not been able to endure the touch of 

 filk, or of the dovvfn of a peach. 



Habit, too, has a powerful influence in modifying the im- 

 prefllsns which we receive from the touch. The heat of a 

 glafs-houfe, which is fuilained u'ithout any unpleafant feeling 

 by the workmen for feveral hours, is intolerable to a perfon 

 unaccufiomcd to it. 



The touch differs from the other fenfes in not requiring a 

 peculiar mode of fenfibility for its exercife ; the hand is 

 rather more ■ fenfible than the reft, of the ilcin, but we can 

 touch with other parts of our furface. In the other fenfes 

 there are peculiar kinds of fenfibihty difpofmg the organs to 

 be afted on by particular obje£ls, and rendering: them 

 ceptible of other imprcilions. The 

 determined by volition, and is generally confequent on the 

 employment of the other fenfes. 



Moft of the other fenfes require an exprefs organic ar- 

 rangement, as well as a peculiar fenfibility in'^he organ ; the 

 touch, on the contra?)', requires only a particular form in 

 its organs. If they have the animal fenfibility, and can em- 

 brace objefls by feveral points, they can dl'.linguifli the tan- 

 gible properties. The touch will be imperfcft, if the organ 

 is in contaft with the body only in one or two points ; yet it 

 will take place. Thus we can touch with the hollo\y of the 

 axilla, at the bend of the elbow, or the knee. But the fenfe 

 is exerted more advantageoufly when the points of contaft 

 arc multiplied. The ftrufture of tl-.o human hand is parti- 

 cularly well contrived in this point of view ; it fliews us that 

 man is calculated, muchinore than tlie animals, for commu- 

 nication with furrounding objcfts ; that the domain of his ani- 

 mal life is therefore much more extenfive ; that his fenfations 

 are more precife, as they pofl'efs an additional means of per- 

 feftion ; that his intellectual faculties are capable of filling 

 an infinitely greater fphere, becaufe tliey are grounded on 

 tke exertion of a much more perfcit orgiui. 



5 "■ 'f^f^ 



ife of the touch is 



The fenfibihty of the fl.in feemsto refide effenCially in f 

 papillx, which is the part of the integuments truly bclongii ;, 

 to the animal life, as the vafcular plexus, compofing the re- 

 ticular body, h connefted with the organic funitions. Its 

 very acute fenfibility requires a proteftion from too (Irong 

 imprefiions; and this is afforded by the epidermis. Wii 

 that is removed, even the impreflitm of the air is pain' 

 and caufes a fenfation, which we call fmarting, which ! 

 longs perhaps exclufively to the dermoid fyftem. It is filt 

 in burns, bliilers, eryfipclas, and in all the inflammations 

 affefiing the reticular body of the (Idn. Itching is another 

 mode of fenfation peculiar to thisfyilem. 



Befides the imprefiions, which teach us the properties of 

 bodies, the exercife of this organ produces feelings of plea- 

 fure and pain. So far as the fenfe of touch is concerned, 

 pleafure may be confidered as that condition of the body, 

 which we fiiould wi(h to have coritinued. The more exquifite 

 feelings of this kind are produced by friftion of the papillx. 

 Without referring to venereal feiflhtions, we may mention a 

 praftice of the Chinefe, of introducing a fmall pencil into 

 the ear and moving it round ib as to excite a very acute plea- 

 furable feehng. 'i'ickhng muft be fomething of this kind ; 

 it is pecuhar to the ikin, and in many individuals excites fen- 

 fations which are a'nioll intolerable. Great diflcrences in 

 this refpeft are obferved in different perfons. Pain is the 

 vi-ry reverf=r of pleafure ; and, in the fl<in, is the moft acute, 

 when the naked organ, where it pofl'effes many papilla;, is 

 irritated. 



The animal fenfibility of the Run, like that of the mucous 

 furfaces, is under the powerful influence of habit, which 

 transforms fucceffively into indifference, and into pleafure 

 what was at firft painful. The air in the fucceffion of the 

 feafons, heat in the various ftates of the atmofphere, water 

 in the bath, or in the humid vapours with which it loads the 

 medium in which we live, our clothes, of which the woollen 

 are at firfl; very unpleafant, in fliort, every thing which afts 

 on the il;in by fimple contaft, produces fenfations wfaich are 

 incefiantly modified by habit. Obferve the varieties of drefs 

 in different countries ; fometimes the upper limbs are un- 

 covered, fometimes the lower ; in fome ir.ftances more or 

 lefs of the trunk is expofed to the air ; often the favage is 

 entirely naked. The parts which are left naked in each 

 people, fupport the contaft of the air without any painful 

 fenfation. Expofe, on the contrary, the parts which are ha- 

 bitually covered, particularly if the atmofphere be cool, a 

 painful fenfation will be produced at firft, but, as the parts 

 become gradually habituated to the contaft, they arc at lall 

 infenfible to it. 



But habit has no power over that heightened ftate of the 

 cutaneous fenfibility, which refults from an organic affeftion, 

 as inflammation for example. The flighteft contaft of a 

 foreign body is extremely painful in this cafe ; and confe- 

 quently the flcin can no longer exert its funftior. of touch. 

 Even the taft, or the power of dillinguifliing general fenfa- 

 tions, is deftroyed. The impreffion of all bodies is uniform ; 

 it'is that of pain. 



The animal fenfibility of the fi<in may be diminiJhed or 

 deftroyed, as in paralyfes ; but the whole organ is never 

 affe .ed ; and in thijjjj refpeft there is very fcldom even 

 hemiplegia. Thefe cafes afford a fiu-ther proof that the 

 cutaneous o^halation and capillary circulation are not in- 

 fluenced by the nerves, fince both go on very well as they 

 do in the paralyfis of the moving organs. 



PropenUs of the Organic Life — Tlie organic fenfibility and 



the inlenfible contraftilitycxilt in the ikin in'avcry highdegree, 



and rtfide jiarticuliu-ly in the exterior capillary fyilem, which 



4 foini) 



