INTEGUMENTS. 



the atmofpliere had no (hare in the produflion of the car- 

 bonic acid gas, bccaufe it was equally great when the ani- 

 mal was confined in gafes containii;g no oxygen ; and l\e 

 therefore concludes, tiiat the carbonic acid gas was exhaled, 

 and the oxygen abforbed. 



On a review of thefe very contradiftory evidences we do 

 not feem to be warranted in believing that any gas is fcpa- 

 rated from the fkin : but perhaps we may conclude that the 

 air in contaft with the organ undergoes a peculiar modifi- 

 cation. 



Scoaccrus Glands of the Siin. — This organ is habitually co- 

 vered .viih an oily fiibltance, whicli occafioiis water to run 

 into globules on the furface of the body, which imparts a 

 greafy liain to linen, when itjjs worn for a long time, and 

 which occafions dull, &c. to adhere to the ikin. This 

 unftuous f ibilance is more abundant in fome pans of the 

 body than in others. About the face it is obferved in con- 

 Cderabh quantities, and on the hairy fcalp. Hence, when 

 perfonal cleanlinefs is not Efficiently attended to, the hair 

 becomes quite greafy and fliiniiig. It is abundant in fitua- 

 tions expofed to friction, as the axillce, perina;um, &c. ; 

 and when confined in inch parts caufes a very difagreeable 

 odour. It is found in very fmall quantity, fo that it can 

 hardly be obferved, in the palms and foles. Certain races 

 of mankir.d, as the negroes, have it in great abundance. 

 Probably the fenlible qualities of the cutaneous difcharge 

 depend in great meafure on this matter, the particular na- 

 ture of which is but httle underftood. It does not feem 

 to undergo thofe chan jcs of augmentation and diminution 

 which are obfervable in the perfpiration. Its obvious utility 

 feems to be that of protefting the llcin from the agency of 

 external caufes, and keeping it in a Hate of foftnefs. 



Is this matter Amply an exhalation from the cutaneous 

 veiTels, or is it produced by glandular apparatus \ In fome 

 parts of the (kin, as about the nofe, and in other fitiiations 

 of the face, the external ear, Sec. there are very manifeft 

 fmall rouiidilh bodies, with a fimple aperture, from which a 

 febaceous matter may be fometimes exprelTed like a fine 

 thread. Morgagni alfo admits their exiftence in the neck, 

 back, perinx im, buttocks, &c. Haller does not conceive 

 tliat they are proved to exift in all parts, and we certainly do 

 not find tliera : yet this oily matter is formed over the whole 

 body. The examples of the fat of the cellular interllices 

 and of the medullary fluid of bones (hew us that the exha- 

 lants can produce matters of this kind. 



P roper tia of the Dermoid Syfem. 



I. Properties refidt'ing from Organization. — Thefe are found 

 to exift in die fliin in a very ftriking degree : the changes of 

 fize, in which diiferent parts, particularly the limbs, fwell 

 to twice or three times their natural bulk, and then recfcvcr 

 their former Itate, prove thefe properties ; and the various 

 tumours, external aneurifms, fudden dillentions from ^reat 

 bruifes, coUeftions of fluid in the abdomen, pregnancy, en- 

 largements of the tefticle, &c. aiford additional proofs. 

 In all thefe cafes the fltin is firft expanded, and then is 

 rellored when the dillending caufe ceafes to aft. A fquare 

 inch of integument lias been found ablejto fuftain a weight 

 of 20olb. 



The contraftihty of the (kin oecafions the retraftion of 

 its edges when it is cut : and this occurs in the dead fub- 

 jcd ; but it feems to l<e heightened by the vital powers as it, 

 occurs to a much greater degree during life. 



Theext'enfibility of the foin is Icfs in many cafes than it 

 would appear to be on firft figiit, as the neighbouring in- 

 teguments are drawn over -a tumour. Thus in large hvell- 



" ings in the fcrofum, the flcin of the penis covers part of the 

 tumour, &c. : in extenfive cicatrices the (kin of the fur- 

 rounding parts is drawn towards the centre of the ulcer. 



- In moil extcnfions the thicknefs of the dermoid tiffue is 

 diminilhed. When it is diftended by the iiifiltration of water 

 in its interllices, as in aiafarca, iti ihickneis mcieifes, while 

 the denfity is diminiftied. It feems to lofe the power of ex- 

 tenfion, fo as to burll under the attion of a dillending 

 caufe, from chronic infl^'inmation. Moft of the chronic 

 affeftions, which alter the tiiTue of this organ, dellroy its 

 contraclile power. 



Vital Properties. 



2. Properties of the yimmal Life. — Animal fenfibility exifts 

 in this orcan in a very high degree : it prefides over the 

 general fenfe of feehiig, wliich is more acute in tliis than 

 in other tiffues, and alfo that of touch, which is very dif- 

 tinft from the former. The general fenfe, called by the 

 French tact, is the power of perceiving the impreifions 

 of furrounding ob'ietls : in this fignification it feems to mean 

 the /ame as the Engiilh word feeling, which is the of&ce of 

 a nerve in general ; as thofe organs only are fo affeAed by ex- 

 ternal bodies as to produce fome change by which the mind is 

 rendered confcious that the bodily organ has been modified. 

 Thus heat and cold, roughncfs and fmoothnefs, hardnefs 

 and foftnefs, moiftnre and drynefs ; preffure caufing pain ; 

 acrid qualities ; titillation producing itching. Sec. are all 

 perceived by the nerves. This kind of tadl belongs to the 

 whole body ; and does not fuppofe any peculiar arrange- 

 ment of the organ ; it is merely the animal fenfibility con- 

 fidered in a Hate of exercife. Thus, when the particular 

 modifications of this fenfibility belonging to the other fenfes 

 have been deftroyed ; when the eye is infenfiblc to light, the 

 ear to founds, &c. the organs ftill retain the power of per- 

 ceiving the prefencc of bodies and their general attributes. 



The fenfe of touch is the power belonging to the fl<;in 

 alone, of examining more minutely and accurately thofe 

 properties of bodies, which we have juil named. For this 

 purpofe we employ chiefly the ends of the fingers ; thofe of 

 the toes feem to be -organized exactly in the lame way, but 

 are incapable of being turned to this ufe by the hardnefs of 

 their coverings. Thefe parts are confpicuous for the fize of 

 their nerves, and for the number and prominence of the pa- 

 ])illa:. This organization gives to them a more exquifite fen- 

 fibility of the fame kind with that belonging to the fkin in ge- 

 n; ra\ The form of the organ in the human fubjeft, where it is 

 compofcd of feveral moveable parts, adapts it particularly to 

 ferve as an inftrumciit of touch, by facilitating its application 

 to external objj^s ; and this advantage may be more particu- 

 larly feen in bodies of a rounded figure.. We rub the fingers 

 gently againft the objeft, fo as \o apply the papillx fuc- 

 ceifively to the different points of its furface. Wliether any 

 phyfical change takes place in the organ, whether the papilla: 

 for example are ereded or no, is entirely unknown. 



The diilinftion of colours by blind perfons, if fuch a 

 power has really exifted in any inftanccs, muft have arifcn 

 from modifications'in the furface produced by the colouring 

 matter. We know that the touch in all cales of blibdneft 

 acquires great acutencfs, as it mult be fo much more cx- 

 ertifed and depended on, than in individuals who can fee. 



The temperature of bodies is eflimated by a comparifuii ; 

 thofe are called cold, which are of a lower temperature than 

 what we had felt immediately before ; and vice vci-fd. Or 

 we refer to the (late of our own furface, and call tlie objects, 

 from which heat palTcs to us, warm, and thofe of the uppo. 

 fite kind cold. The fame fluid will appear cold to one h<uid 

 G£ 2 imd 



