Document GQ7agZME5BK6MGn3O9kVa1Br

c& 11to4 In nor**! alaoa|.iwr.i for an additional 24 month*. Exposure for 14 month* we* ourriotoat to produo* cellular accumulation* of phagoj^Jfcpa around terminal bronahiolo* and peripheral arteriole* tog*thor with aoa* pact collections of similar colls In the traeheobronehlal lymph nodes. At that tire thoro tore no typical atbcstoal* bod loo, but smooth, polntod, yellow fiber* wore soan eery raroly. With continued exposure, up to 42 month*, reaction in the loeetlooo noted progressed to the formation of oollular connective tie sue which made well-defined sheath* about the respiratory bronchiole* and artorlolea, marked lymphoid hyperplasia and lynphold infiltration of hronchtolar wall* (fit. 10). Typical aabeafeaal* bodies wero sot formed although there was an oocaalonal fiber, smooth, yellow and polnlod. Pleurisy waa not present. The roaotienwa* similar In location to that In tho guinea pigs, but flbrosla was much slower in do/olopoont. Iuwmlgenograrae of cat* made after exposure-period* of 33 and 42 montha, rospootlvely, Tailed to, denonotrato evidence of pulsonary pathology. Reaction In Hots. Although 20 rat* woro placed In the dust room, many died from pneumonia and were not eultablo for study. Fire animals, of which one wte exposed for 19 month* and four for.* 25 month*, were free . from pulmonary Infection and offer a basis for tentative conclusion*. Inthe 19-monthsanimal, tho reaction was Juet beginning. All four animal* wseerlflood at 2f month* showod a well-marked peribronchiolar fibrosiu- Affor * long eoaroh only two email smooth aahostoals bodloe wore fourtit In the 19-montha animal and none was found In the 25-month* animal. Thud, those animals exhibited flbroot* without aobostosla bodies or fibrosed aecCMpantod by only a very infrequent aabestoale body. e T LlV