Document ZBbZjNawzYw9E4YQv6e1GBXGV

c t4 In th atmosphere brAtlioJ| oaoond, ltr{Q particles ore more offootUtly removed by the protective tieahenlsa* of tho upper respiratory tract. In the ceao of fibrous materials theso faotore have loes influence and fibero 100 end ovon 00 ulcrona In lonr.th hero beon found in tho terminal air cpacos of human lungs. In snail laboratory animal exposed to asbettoe dust tho maximum longth of flbor found in tho lung raroly exceods CO elcrons. A largo proportion of non-fibroue partioulato duat Inhaled into tho lung la found in tho terminal air apaoos (alveolar duct, atrtu, alvooll) In all parts oC tho organ} In contract, inhaled asbestos fiber* oro .firat diaooverod in tho roopiratory bronchioles. Thoas snail paasago* or# 1Mdlatoly distil to bronohioloo lined hy ciliated eplthellum(6). Their own oasentlel lining ia a low ouboldal typo of eolthelluA but, ao their name implies, thoy actually function in reaplration through lateral alveo li distributed along their trails. Either these alveoli or tho abrupt * * change in tho charaotor of the lining epithelium*or the email diameter of tho roopiratory bronchiole or the combination of all three faotors Is re sponsible for rotontlon of the fiber at this sito. Only after asbastoslc is well established are appreciable numbers of fibers aeon la the moro peripheral air apaoes. further explanation la roqulrod to clarity this observation, Hate of Tlaauo Reaction to Asbestoa fibers. The tissue reaction to asbestos develops much core rapidly than dooo tho reaction to quarts dust. 6, UUlor, Klliiam 3,i Tho Urng, Charles C, Thomas, Publishers, 1937. % *6* V^ T