1 8 9 0 ▁as ▁a ▁temporary ▁w ors ening ▁of ▁vision ▁with ▁exercise ▁in ▁patients ▁with ▁opt ic ▁neur itis . ▁Later ▁research ▁revealed ▁the ▁link ▁between ▁ne uro log ical ▁signs ▁such ▁as ▁visual ▁loss ▁and ▁increased ▁heat ▁production ▁and ▁U h th off ' s ▁belief ▁that ▁exercise ▁was ▁the ▁et i ology ▁of ▁visual ▁loss ▁was ▁replaced ▁by ▁the ▁conclus ions ▁of ▁these ▁later ▁research ers ▁stating ▁that ▁heat ▁was ▁the ▁prime ▁et i ology . ▁ ▁References ▁▁ ▁Category : Sym pt oms ▁and ▁signs : ▁N erv ous ▁system ▁Category : Auto imm une ▁dise ases ▁Category : Multi ple ▁s cl eros is <0x0A> </s> ▁A ▁fix ative ▁is ▁used ▁to ▁equal ize ▁the ▁v apor ▁press ures , ▁and ▁thus ▁the ▁vol at ilities , ▁of ▁the ▁raw ▁materials ▁in ▁a ▁perf ume ▁oil , ▁as ▁well ▁as ▁to ▁increase ▁the ▁ten acity . ▁ ▁Natural ▁fix atives ▁are ▁res ino ids ▁( ben zo in , ▁lab dan um , ▁my r rh , ▁o lib an um , ▁stor ax , ▁to lu ▁b als am ) ▁and ▁animal ▁products ▁( am ber gr is , ▁cast ore um , ▁mus k , ▁and ▁civ et ). ▁Syn th etic ▁fix atives ▁include ▁subst ances ▁of ▁low ▁vol at ility ▁( di phen yl m eth ane , ▁cy c lop ent ade can ol ide , ▁amb ro x ide , ▁ben zy l ▁sal ic yl ate ) ▁and ▁virt ually