Document Z4g2nR6QG2wbzGe7kqXnrNmkZ

640 EXPERIMENTAL ASBESTOSIS--GROSS A DE TREVILLE Fig 1.--Ash pattern of odd-insoluble material in lung of rat immediately following Intretrecheal injec tion of chiysotlle dust. Alveolar ducts , are outlined by fairly thick, continuous coating of dust. Some dust, mostly in the form of discontinuous deposits. Is also found In some distal alveoli. Section was subjected to microincineration followed by treatment with concen trated hydrochloric acid (X 150). ately after the intratracheal injection of chryaotile, the dust was seen applied as a uniform and continuous, dense coating upon the respiratory surfaces of the alveolar ducts and their evaginating alveoli (Fig 1). The lumens were everywhere widely patent. Sur face coating by the dust of some of the distal alveoli was also observed, but not regularly. After 72 hours, the proximal portion of the raoemus6 was a nearly solid, cellular structure in which the lumens of the respira tory bronchiole and alveolar ducts were oblit erated by a polypoid mass of ovoid and plump spindle-shaped cells which also oblit erated the lumens of the evaginating al veoli. A highly significant change in the distribution of the asbestos dust was now Fig Ash pattern of acid-insoluble materiel, three days after intratracheal Injection of chryaotile dust In rat. Dust, now in the form of flocculent masses of splculated aggregates, seems to form casts of alveolar ducts and fills their lumens. Very little dust is noted in the peripheral alveoli (X 150). observed. The dust permeated the occlusive inflammatory tissue and thereby formed a cast of what was once the lumen (Fig 2). It was, however, no longer oompactly disposed; rather, it was distributed in a flocculent manner. Nevertheless, the total amount of dust in the lumens of the alveolar ducts ap peared to be considerably greater three days after the intratracheal injection than that present immediately after the injection. At the same time, less asbestos dust was ob served in the more peripherally situated al veoli. It is probable that the increase in the amount of dust in the alveolar ducts was de rived from the more peripheral alveoli. Al though some of the finer dust may have been intracellular, the greater bulk, by far, was extracellular, being imprisoned in the inter- Arch Erwiron Health--VoI 15. Nov 1967 8005 1460 PRODUCED BY FORD