e　organ　of　taste　must　be　liquefied；　and　so　to　start　with　must　be　non…liquid　but　capable　of　liquefaction　without　loss　of　its　distinctive　nature。　This　is　confirmed　by　the　fact　that　the　tongue　cannot　taste　either　when　it　is　too　dry　or　when　it　is　too　moist；　in　the　latter　case　what　occurs　is　due　to　a　contact　with　the　pre…existent　moisture　in　the　tongue　itself；　when　after　a　foretaste　of　some　strong　flavour　we　try　to　taste　another　flavour；　it　is　in　this　way　that　sick　persons　find　everything　they　taste　bitter；　viz。　because；　when　they　taste；　their　tongues　are　overflowing　with　bitter　moisture。　　　The　species　of　flavour　are；　as　in　the　case　of　colour；　（a）　simple；　i。e。　the　two　contraries；　the　sweet　and　the　bitter；　（b）　secondary；　viz。　（i）　on　the　side　of　the　sweet；　the　succulent；　（ii）　on　the　side　of　the　bitter；　the　saline；　（iii）　between　these　come　the　pungent；　the　harsh；　the　astringent；　and　the　acid；　these　pretty　well　exhaust　the　varieties　of　flavour。　It　follows　that　what　has　the　power　of　tasting　is　what　is　potentially　of　that　kind；　and　that　what　is　tasteable　is　what　has　the　power　of　making　it　actually　what　it　itself　already　is。
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  Whatever　can　be　said　of　what　is　tangible；　can　be　said　of　touch；　and　vice　versa；　if　touch　is　not　a　single　sense　but　a　group　of　senses；　there　must　be　several　kinds　of　what　is　tangible。　It　is　a　problem　whether　touch　is　a　single　sense　or　a　group　of　senses。　It　is　also　a　problem；　what　is　the　organ　of　touch；　is　it　or　is　it　not　the　flesh　（including　what　in　certain　animals　is　homologous　with　flesh）？　On　the　second　view；　flesh　is　'the　medium'　of　touch；　the　real　organ　being　situated　farther　inward。　The　problem　arises　because　the　field　of　each　sense　is　according　to　the　accepted　view　determined　as　the　range　between　a　single　pair　of　contraries；　white　and　black　for　sight；　acute　and　grave　for　hearing；　bitter　and　sweet　for　taste；　but　in　the　field　of　what　is　tangible　we　find　several　such　pairs；　hot　cold；　dry　moist；　hard　soft；　&c。　This　problem　finds　a　partial　solution；　when　it　is　recalled　that　in　the　case　of　the　other　senses　more　than　one　pair　of　contraries　are　to　be　met　with；　e。g。　in　sound　not　only　acute　and　grave　but　loud　and　soft；　smooth　and　rough；　&c。；　there　are　similar　contrasts　in　the　field　of　colour。　Nevertheless　we　are　unable　clearly　to　detect　in　the　case　of　touch　what　the　single　subject　is　which　underlies　the　contrasted　qualities　and　corresponds　to　sound　in　the　case　of　hearing。　　　To　the　question　whether　the　organ　of　touch　lies　inward　or　not　（i。e。　whether　we　need　look　any　farther　than　the　flesh）；　no　indication　in　favour　of　the　second　answer　can　be　drawn　from　the　fact　that　if　the　object　comes　into　contact　with　the　flesh　it　is　at　once　perceived。　For　even　under　present　conditions　if　the　experiment　is　made　of　making　a　web　and　stretching　it　tight　over　the　flesh；　as　soon　as　this　web　is　touched　the　sensation　is　reported　in　the　same　manner　as　before；　yet　it　is　clear　that　the　or　is　gan　is　not　in　this　membrane。　If　the　membrane　could　be　grown　on　to　the　flesh；　the　report　would　travel　still　quicker。　The　flesh　plays　in　touch　very　much　the　same　part　as　would　be　played　in　the　other　senses　by　an　air…envelope　growing　round　our　body；　had　we　such　an　envelope　attached　to　us　we　should　have　supposed　that　it　was　by　a　single　organ　that　we　perceived　sounds；　colours；　and　smells；　and　we　should　have　taken　sight；　hearing；　and　smell　to　be　a　single　sense。　But　as　it　is；　because　that　through　which　the　different　movements　are　transmitted　is　not　naturally　attached　to　our　bodies；　the　difference　of　the　various　sense…organs　is　too　plain　to　miss。　But　in　the　case　of　touch　the　obscurity　remains。　　　There　must　be　such　a　naturally　attached　'medium'　as　flesh；　for　no　living　body　could　be　constructed　of　air　or　water；　it　must　be　something　solid。　Consequently　it　must　be　composed　of　earth　along　with　these；　which　is　just　what　flesh　and　its　analogue　in　animals　which　have　no　true　flesh　tend　to　be。　Hence　of　necessity　the　medium　through　which　are　transmitted　the　manifoldly　contrasted　tactual　qualities　must　be　a　body　naturally　attached　to　the　organism。　That　they　are　manifold　is　clear　when　we　consider　touching　with　the　tongue；　we　apprehend　at　the　tongue　all　tangible　qualities　as　well　as　flavour。　Suppose　all　the　rest　of　our　flesh　was；　like　the　tongue；　sensitive　to　flavour；　we　should　have　identified　the　sense　of　taste　and　the　sense　of　touch；　what　saves　us　from　this　identification　is　the　fact　that　touch　and　taste　are　not　always　found　together　in　the　same　part　of　the　body。　The　following　problem　might　be　raised。　Let　us　assume　that　every　body　has　depth；　i。e。　has　three　dimensions；　and　that　if　two　bodies　have　a　third　body　between　them　they　cannot　be　in　contact　with　one　another；　let　us　remember　that　what　is　liquid　is　a　body　and　must　be　or　contain　water；　and　that　if　two　bodies　touch　one　another　under　water；　their　touching　surfaces　cannot　be　dry；　but　must　have　water　between；　viz。　the　water　which　wets　their　bounding　surfaces；　from　all　this　it　follows　that　in　water　two　bodies　cannot　be　in　contact　with　one　another。　The　same　holds　of　two　bodies　in　air…air　being　to　bodies　in　air　precisely　what　water　is　to　bodies　in　water…but　the　facts　are　not　so　evident　to　our　observation；　because　we　live　in　air；　just　as　animals　that　live　in　water　would　not　notice　that　the　things　which　touch　one　another　in　water　have　wet　surfaces。　The　problem；　then；　is：　does　the　perception　of　all　objects　of　sense　take　place　in　the　same　way；　or　does　it　not；　e。g。　taste　and　touch　requiring　contact　（as　they　are　commonly　thought　to　do）；　while　all　other　senses　perceive　over　a　distance？　The　distinction　is　unsound；　we　perceive　what　is　hard　or　soft；　as　well　as　the　objects　of　hearing；　sight；　and　smell；　through　a　'medium'；　only　that　the　latter　are　perceived　over　a　greater　distance　than　the　former；　that　is　why　the　facts　escape　our　notice。　For　we　do　perceive　everything　through　a　medium；　but　in　these　cases　the　fact　escapes　us。　Yet；　to　repeat　what　we　said　before；　if　the　medium　for　touch　were　a　membrane　separating　us　from　the　object　without　our　observing　its　existence；　we　should　be　relatively　to　it　in　the　same　condition　as　we　are　now　to　air　or　water　in　which　we　are　immersed；　in　their　case　we　fancy　we　can　touch　objects；　nothing　coming　in　between　us　and　them。　But　there　remains　this　difference　between　what　can　be　touched　and　what　can　be　seen　or　can　sound；　in　the　latter　two　cases　we　perceive　because　the　medium　produces　a　certain　effect　upon　us；　whereas　in　the　perception　of　objects　of　touch　we　are　affected　not　by　but　along　with　the　medium；　it　is　as　if　a　man　were　struck　through　his　shield；　where　the　shock　is　not　first　given　to　the　shield　and　passed　on　to　the　man；　but　the　concussion　of　both　is　simultaneous。　　　In　general；　flesh　and　the　tongue　are　related　to　the　real　organs　of　touch　and　taste；　as　air　and　water　are　to　those　of　sight；　hearing；　and　smell。　Hence　in　neither　the　one　case　nor　the　other　can　there　be　any　perception　of　an　object　if　it　is　placed　immediately　upon　the　organ；　e。g。　if　a　white　object　is　placed　on　the　surface　of　the　eye。　This　again　shows　that　what　has　the　power　of　perceiving　the　tangible　is　seated　inside。　Only　so　would　there　be　a　complete　analogy　with　all　the　other　senses。　In　their　case　if　you　place　the　object　on　the　organ　it　is　not　perceived；　here　if　you　place　it　on　the　flesh　it　is　perceived；　therefore　flesh　is　not　the　organ　but　the　medium　of　touch。　　　What　can　be　touched　are　distinctive　qualities　of　body　as　body；　by　such　differences　I　mean　those　which　characterize　the　elements；　viz；　hot　cold；　dry　moist；　of　which　we　have　spoken　earlier　in　our　treatise　on　the　elements。　The　organ　for　the　perception　of　these　is　that　of　touch…that　part　of　the　body　in　which　primarily　the　sense　of　touch　resides。　This　is　that　part　which　is　potentially　such　as　its　object　is　actually：　for　all　sense…perception　is　a　process　of　being　so　affected；　so　that　that　which　makes　something　such　as　it　itself　actually　is　makes　the　other　such　because　the　other　is　already　potentially　such。　That　is　why　when　an　object　of　touch　is　equally　hot　and　cold　or　hard　and　soft　we　cannot　perceive；　what　we　perceive　must　have　a　degree　of　the　sensible　quality　lying　beyond　the　neutral　point。　This　implies　that　the　sense　itself　is　a　'mean'　between　any　two　opposite　qualities　which　determine　the　field　of　that　sense。　It　is　to　this　that　it　owes　its　power　of　discerning　the　objects　in　that　field。　What　is　'in　the　middle'　is　fitted　to　discern；　relatively　to　either　extreme　it　can　put　itself　in　the　place　of　the　other。　As　what　is　to　perceive　both　white　and　black　must；　to　begin　with；　be　actually　neither　but　potentially　either　（and　so　with　all　the　other　sense…organs）；　so　the　organ　of　touch　must　be　neither　hot　nor　cold。　　　Further；　as　in　a　sense　sight　had　for　its　object　both　what　was　visible　and　what　was　invisible　（and　there　was　a　parallel　truth　about　all　the　other　senses　discussed）；　so　touch　has　for　its　object　both　what　is　tangible　and　what　is　intangible。　Here　by　'intangible'　is　meant　（a）　what　like　air　possesses　some　quality　of　tangible　things　in　a　very　slight　degree　and　（b）　what　possesses　it　in　an　excessive　degree；　as　destructive　things　do。　　　We　have　now　given　an　outline　account　of　each　of　the　several　senses。
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  The　following　results　applying　to