SEN 



SENSAON, a town of Africa, in the kingdom of Fez, 

 near a mountain of the fame name ; 25 miles S. of Tetuan. 



SENSATION, in Phyliology, a general term denoting 

 the cffeft produced in the mind by the impreffions of exter- 

 nal bodies on our organs of fenfe, by various changes in the 

 internal organs, and by affeftions of any paits of the body 

 which poffefs nerves. The appropriate external objefts, 

 being prefented to the eyes, ears, nofe, tongue, or ikin, 

 give us the fenfations of which thofe parts are refpedively 

 the organs: hunger and thirlt, naufea and ficknefs, griping, 

 fainting, agitation, &c. are the refults of particular ftates 

 of internal organs ; fatigue is caufed by exertion of the 

 mufcular fyftem ; mechanical or chemical applications to any 

 parts pofleffing nerves caufe pains of all kinds and degrees. 

 Thus feeing, hearing, fmelling, tailing, and touching ; 

 hunger and thirlt, ficknefs, fainting, &c. ; and all the 

 agreeable or difagreeable effefts produced by external ob- 

 jefts afting on our frame, are fo many modea of fenfation, 

 fo many tlates of exiftence, accompanied each with a peculiar 

 feeling or aft of confcioufnefs. 



In the five fenfes, fenfation requires a healthy condition 

 of the external organs of the brain, and of the nerves which 

 pafs between the organs and the brain. The abfence of 

 either of thofe conditions deltroys fenfations : if the optic 

 nerve be divided there is no feeing, although the eye and 

 brain be healthy ; if the brain be comprefTed, the nerve and 

 the eye remaining unafFefted ; or if the eye be difeafed, the 

 nerve and the brain being found, vifion is deltroyed. The 

 fame is the cafe with the general feeling of the frame : if 

 the nerves of a limb be divided, or the brain be compreflcd, 

 there is no fenfation ; a pin might be thruft into the part 

 without being felt. The dependance of the internal feelings 

 on the brain is not fo clearly made out in every inftance. On 

 the whole, however, phyfiologills confider it as eftablifhed, 

 that fenfation is the funftion of the nervous fyltem. On this 

 fubjeft, as well as on the phenomena of fenfation exhibited 

 by the brain and nerves, we refer to Brain, Phyfwlogy of 

 the, to Life, and Nervous Syjiem. 



As there are fo many different phenomena included under 

 the common term of fenfation, what is the point in which 

 they agree ? What is the charafter by which they are all re- 

 cognized as fenfations ? It is the feehng excited, the con- 

 fcioufnefs of a new mode of exiltence, the modification 

 which the fentient being experiences. Senfation ia (hort is 

 feeling. 



This is the only point in which the various fenfations agree ; 

 independently of this there is httle lefemblance, or even ana- 

 logy between them. Hearing is no more hke feeing, and 

 either of thefe is no more like hunger or thirft, than a 

 inufcle is to a nerve or the fl{in. 



Senfations may be reproduced without any external ob- 

 jefts, by an aftive ftate of the brain : thus in dreams we 

 pafs through fcenes, and experience feebngs, which are not 

 diftinguifhable from real occurrences. 



Senfation, according to Dr. Reid, is a name given by phi- 

 lofophers to an aft of mind, which may be diftinguilhed from 

 all others by this, that it hath no objeft dilliuft from the 

 aft itfelf. Pain of every kind is an uneafy fenfation. The 

 pain and the feeling, he fays, are one and the fame thing ; 

 and cannot be disjoined even in imagination. Pain, when 

 it is not felt, has no exiltence. The fame obfervation may 

 be applied to every other fenfation. This author adds, that 

 when we have acquired a diftinft notion of that fimple aft 

 of the mind called fenfation, we ftiall be able the more 

 eafily to diftinguidi it from every external objeft that 

 accompanies it, and from every other aft of the mind that 

 may be conjoined with it. Hence it is of importance, that 



SEN 



the name of fenfation fhould, in philofophical writings, fie 

 appropriated to fignify this fimple aft of the mind, wicnout 

 including any thing more in its fignification, or being ap- 

 plied to other purpofes. The word feeling, which figmfies 

 the perceptions we have of external objefts by the fenfe of 

 touch, is alfo uied to denote the fame thing as fenlation r in 

 wliich fenfe it has no objeft, the feeling and the thing felt 

 being one and the fame. He acknowledges, howe/er, that 

 betwixt feeling, taken in this lall fenfe, and fenlation, thifre 

 may be this faall difference ; that fenfation is moft com- 

 monly ufed to fignify thofe feelings which refult from our 

 external fenfes and bodily appetites, and all onr bodily 

 pains and pleafures. But there are feelings of a noblrr iia- 

 ture, accompanying our affeftions, our moral judgments, 

 and our determinations in matters of talte, to which the 

 word fenfation is lefs properly applied. 



Dr. Reid, in another place, obferves, that almolt all our 

 perceptions have correfponding fenfations, which conftantly 

 accompany them, and, on that account, are very apt to be 

 confounded with them. Hence the names of moll of our 

 fenfations become ambiguous, and this ambiguity hath 

 very much perplexed philofophers. He alleges feveral 

 fafts that ferve to illuflrate and evince this ambiguity, in re- 

 ference to the names we have for fmells, taftes, founds, and 

 for the various degrees of heat and cold, which names denote 

 both a fenfation, and a quality perceived by means of that 

 fenfation. The caufe is the fame with refpeft to many ope- 

 rations of mind to which we give one name, and which we 

 always confider as one thing ; and yet they are complex in 

 their nature, and made up of feveral more fimple ingredients ; 

 of which ingredients fenfation ver^* often reck<ins one. In- 

 deed, the number of our fenfations and feelings is prodi- 

 gious ; and the molt general and important divilion of them 

 is into the agreeable, the difagreeable, and the indifferent. 



The preceding remarks ferve to evince the importance of 

 diftinguifhing carefully between our fenfations and that jjer- 

 ception of external objefts which is conllantly conjoined 

 with them. Senfation, fays this author, taken by itfelf, im- 

 plies neither the conception nor belief of any external ob- 

 jeft. It_ fuppofes a fentient being, and a certain manner in 

 which that being is affefted, but it fuppofes no more. But 

 perception, in his view of it, implies an immediate convic- 

 tion and belief of fomething external ; fomething different 

 both from the mind that perceives and from the aft of per- 

 ception. Things fo different in their nature ought to be 

 dillinguifhed ; but by our conltitution they are always united. 

 Every different perception is conjoined with 3 fenfation that 

 is proper to it. The one is the fign, the other the thing 

 fignified. They coalefce in our imagination ; they are fig- 

 nitied by one name, and are confidered as one fimple ope- 

 ration. To the philofopher it belongs to dillinguifh between 

 them. 



Our author elfewhere obferves, that when certain impref- 

 fions are made upon our organs, nerves, and brain, certain 

 correfponding fenfations are felt, and certain objefts are 

 both conceived and believed to exift. But wc can neither dif- 

 cover the caufe of any one of thefe operations, nor any ne- 

 ceiiary conneftion of one with another. 



On the fubjeft of this article, in its conneftion with meta- 

 phyfics, or the philofophy of the human mind, we refer to 

 Idea, Perception, ilf«i/a/ Philosoi'HV, Vi oration, and 

 other terms of a fimilar import, or in any degree connefted 

 with them, occurring in various parts of the Cyclopedia. 



SENSBURG, in Geography, a town of PruiTia, in the 

 province of Bartenland ; 14 miles S. of Raftenburg. N. 

 lat. 53°44'. E. long. zi° 23'. 



SENSE. Senses, in Phj/fiole^y and jinatomy, the or- 

 gans 



