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mingled　with　irregularity；　and　smoothness　is　produced　by　the　joint

effect　of　uniformity　and　density。

　　The　most　important　of　the　affections　which　concern　the　whole　body

remains　to　be　considered…that　is；　the　cause　of　pleasure　and　pain　in

the　perceptions　of　which　I　have　been　speaking；　and　in　all　other　things

which　are　perceived　by　sense　through　the　parts　of　the　body；　and　have

both　pains　and　pleasures　attendant　on　them。　Let　us　imagine　the

causes　of　every　affection；　whether　of　sense　or　not；　to　be　of　the

following　nature；　remembering　that　we　have　already　distinguished

between　the　nature　which　is　easy　and　which　is　hard　to　move；　for　this

is　the　direction　in　which　we　must　hunt　the　prey　which　we　mean　to　take。

A　body　which　is　of　a　nature　to　be　easily　moved；　on　receiving　an

impression　however　slight；　spreads　abroad　the　motion　in　a　circle；

the　parts　communicating　with　each　other；　until　at　last；　reaching　the

principle　of　mind；　they　announce　the　quality　of　the　agent。　But　a

body　of　the　opposite　kind；　being　immobile；　and　not　extending　to　the

surrounding　region；　merely　receives　the　impression；　and　does　not

stir　any　of　the　neighbouring　parts；　and　since　the　parts　do　not

distribute　the　original　impression　to　other　parts；　it　has　no　effect　of

motion　on　the　whole　animal；　and　therefore　produces　no　effect　on　the

patient。　This　is　true　of　the　bones　and　hair　and　other　more　earthy

parts　of　the　human　body；　whereas　what　was　said　above　relates　mainly　to

sight　and　hearing；　because　they　have　in　them　the　greatest　amount　of

fire　and　air。　Now　we　must　conceive　of　pleasure　and　pain　in　this　way。

An　impression　produced　in　us　contrary　to　nature　and　violent；　if

sudden；　is　painful；　and；　again；　the　sudden　return　to　nature　is

pleasant；　but　a　gentle　and　gradual　return　is　imperceptible　and　vice

versa。　On　the　other　hand　the　impression　of　sense　which　is　most

easily　produced　is　most　readily　felt；　but　is　not　accompanied　by

Pleasure　or　pain；　such；　for　example；　are　the　affections　of　the

sight；　which；　as　we　said　above；　is　a　body　naturally　uniting　with　our

body　in　the　day…time；　for　cuttings　and　burnings　and　other

affections　which　happen　to　the　sight　do　not　give　pain；　nor　is　there

pleasure　when　the　sight　returns　to　its　natural　state；　but　the

sensations　are　dearest　and　strongest　according　to　the　manner　in

which　the　eye　is　affected　by　the　object；　and　itself　strikes　and

touches　it；　there　is　no　violence　either　in　the　contraction　or　dilation

of　the　eye。　But　bodies　formed　of　larger　particles　yield　to　the　agent

only　with　a　struggle；　and　then　they　impart　their　motions　to　the

whole　and　cause　pleasure　and　pain…pain　when　alienated　from　their

natural　conditions；　and　pleasure　when　restored　to　them。　Things　which

experience　gradual　withdrawings　and　emptyings　of　their　nature；　and

great　and　sudden　replenishments；　fail　to　perceive　the　emptying；　but

are　sensible　of　the　replenishment；　and　so　they　occasion　no　pain；　but

the　greatest　pleasure；　to　the　mortal　part　of　the　soul；　as　is

manifest　in　the　case　of　perfumes。　But　things　which　are　changed　all　of

a　sudden；　and　only　gradually　and　with　difficulty　return　to　their　own

nature；　have　effects　in　every　way　opposite　to　the　former；　as　is

evident　in　the　case　of　burnings　and　cuttings　of　the　body。

　　Thus　have　we　discussed　the　general　affections　of　the　whole　body；　and

the　names　of　the　agents　which　produce　them。　And　now　I　will　endeavour

to　speak　of　the　affections　of　particular　parts；　and　the　causes　and

agents　of　them；　as　far　as　I　am　able。　In　the　first　place　let　us　set

forth　what　was　omitted　when　we　were　speaking　of　juices；　concerning　the

affections　peculiar　to　the　tongue。　These　too；　like　most　of　the　other

affections；　appear　to　be　caused　by　certain　contractions　and　dilations；

but　they　have　besides　more　of　roughness　and　smoothness　than　is　found

in　other　affections；　for　whenever　earthy　particles　enter　into　the

small　veins　which　are　the　testing　of　the　tongue；　reaching　to　the

heart；　and　fall　upon　the　moist；　delicate　portions　of　flesh…when；　as

they　are　dissolved；　they　contract　and　dry　up　the　little　veins；　they

are　astringent　if　they　are　rougher；　but　if　not　so　rough；　then　only

harsh。　Those　of　them　which　are　of　an　abstergent　nature；　and　purge

the　whole　surface　of　the　tongue；　if　they　do　it　in　excess；　and　so

encroach　as　to　consume　some　part　of　the　flesh　itself；　like　potash

and　soda；　are　all　termed　bitter。　But　the　particles　which　are　deficient

in　the　alkaline　quality；　and　which　cleanse　only　moderately；　are　called

salt；　and　having　no　bitterness　or　roughness；　are　regarded　as　rather

agreeable　than　otherwise。　Bodies　which　share　in　and　are　made　smooth　by

the　heat　of　the　mouth；　and　which　are　inflamed；　and　again　in　turn

inflame　that　which　heats　them；　and　which　are　so　light　that　they　are

carried　upwards　to　the　sensations　of　the　head；　and　cut　all　that

comes　in　their　way；　by　reason　of　these　qualities　in　them；　are　all

termed　pungent。　But　when　these　same　particles；　refined　by

putrefaction；　enter　into　the　narrow　veins；　and　are　duly　proportioned

to　the　particles　of　earth　and　air　which　are　there；　they　set　them

whirling　about　one　another；　and　while　they　are　in　a　whirl　cause　them

to　dash　against　and　enter　into　one　another；　and　so　form　hollows

surrounding　the　particles　that　enter…which　watery　vessels　of　air

（for　a　film　of　moisture；　sometimes　earthy；　sometimes　pure；　is　spread

around　the　air）　are　hollow　spheres　of　water；　and　those　of　them　which

are　pure；　are　transparent；　and　are　called　bubbles；　while　those

composed　of　the　earthy　liquid；　which　is　in　a　state　of　general

agitation　and　effervescence；　are　said　to　boil　or　ferment…of　all

these　affections　the　cause　is　termed　acid。　And　there　is　the　opposite

affection　arising　from　an　opposite　cause；　when　the　mass　of　entering

particles；　immersed　in　the　moisture　of　the　mouth；　is　congenial　to

the　tongue；　and　smooths　and　oils　over　the　roughness；　and　relaxes　the

parts　which　are　unnaturally　contracted；　and　contracts　the　parts

which　are　relaxed；　and　disposes　them　all　according　to　their

nature…that　sort　of　remedy　of　violent　affections　is　pleasant　and

agreeable　to　every　man；　and　has　the　name　sweet。　But　enough　of　this。

　　The　faculty　of　smell　does　not　admit　of　differences　of　kind；　for

all　smells　are　of　a　half　formed　nature；　and　no　element　is　so

proportioned　as　to　have　any　smell。　The　veins　about　the　nose　are　too

narrow　to　admit　earth　and　water；　and　too　wide　to　detain　fire　and

air；　and　for　this　reason　no　one　ever　perceives　the　smell　of　any　of

them；　but　smells　always　proceed　from　bodies　that　are　damp；　or

putrefying；　or　liquefying；　or　evaporating；　and　are　perceptible　only　in

the　intermediate　state；　when　water　is　changing　into　air　and　air　into

water；　and　all　of　them　are　either　vapor　or　mist。　That　which　is　passing

out　of　air　into　water　is　mist；　and　that　which　is　passing　from　water

into　air　is　vapour；　and　hence　all　smells　are　thinner　than　water　and

thicker　than　air。　The　proof　of　this　is；　that　when　there　is　any

obstruction　to　the　respiration；　and　a　man　draws　in　his　breath　by

force；　then　no　smell　filters　through；　but　the　air　without　the　smell

alone　penetrates。　Wherefore　the　varieties　of　smell　have　no　name；　and

they　have　not　many；　or　definite　and　simple　kinds；　but　they　are

distinguished　only　painful　and　pleasant；　the　one　sort　irritating　and

disturbing　the　whole　cavity　which　is　situated　between　the　head　and　the

navel；　the　other　having　a　soothing　influence；　and　restoring　this

same　region　to　an　agreeable　and　natural　condition。

　　In　considering　the　third　kind　of　sense；　hearing；　we　must　speak　of

the　causes　in　which　it　originates。　We　may　in　general　assume　sound　to

be　a　blow　which　passes　through　the　ears；　and　is　transmitted　by　means

of　the　air；　the　brain；　and　the　blood；　to　the　soul；　and　that　hearing　is

the　vibration　of　this　blow；　which　begins　in　the　head　and　ends　in　the

region　of　the　liver。　The　sound　which　moves　swiftly　is　acute；　and　the

sound　which　moves　slowly　is　grave；　and　that　which　is　regular　is

equable　and　smooth；　and　the　reverse　is　harsh。　A　great　body　of　sound　is

loud；　and　a　small　body　of　sound　the　reverse。　Respecting　the

harmonies　of　sound　I　must　hereafter　speak。

　　There　is　a　fourth　class　of　sensible　things；　having　many　intricate

varieties；　which　must　now　be　distinguished。　They　are　called　by　the

general　name　of　colours；　and　are　a　flame　which　emanates　from　every

sort　of　body；　and　has　particles　corresponding　to　the　sense　of　sight。　I

have　spoken　already；　in　what　has　preceded；　of　the　causes　which

generate　sight；　and　in　this　place　it　will　be　natural　and　suitable　to

give　a　rational　theory　of　colours。

　　Of　the　particles　coming　from　other　bodies　which　fall　upon　the　sight；

some　are　smaller　and　some　are　larger；　and　some　are　equal　to　the

parts　of　the　sight　itself。　Those　which　are　equal　are　imperceptible；

and　we　call　them　transparent。　The　larger　produce　contraction；　the

smaller　dilation；　in　the　sight；　exercising　a　power　akin　to　that　of　hot

and　cold　bodies　on　the　flesh；　or　of　astringent　bodies　on　the　tongue；

or　of　those　heating　bodies　which　we　termed　pungent。　White　and　black

are　similar　effects　of　contraction　and　dilation　in　another　sphere；　and

for　this　reason　have　a　different　appearance。　Wherefore；　we　ought　to

term　white　that　which　dilates　the　visual　ray；　and　the　opposite　of　this

is　black。　There　is　also　a　swifter　motion　of　a　different　sort　of　fire

which　strikes　and　dilates　the　ray　of　sight　until　it　reaches　the

eyes；　forcing　a　way　through　their　passages　and　melting　them；　and

eliciting　from　them　a　union　of　fire　and　water　which　we　call　tears；

being　itself　an　opposite　fire　which　comes　to　them　from　an　opposite

direction…the　inner　fire　flashes　forth　like　lightning；　and　the　outer

finds　a　way　in　and　is　extinguished　in　the　moisture；　and　all　sorts　of

colours　are　generated　by　the　mixture。　This　affection　is　termed

dazzling；　and　the　object　which　produces　it　is　called　bright　and

flashing。　There　is　another　sort　of　fire　which　is　intermediate；　and

which　reaches　and　mingles　with　the　moisture　of　the　eye　without

flashing；　and　in　this；　the　fire　mingling　with　the　ray　of　the　moisture；

produces　a　colour　like　blood；　to　which　we　give　t