Document 445w8o2wXBrpddVq6q4kYmYqV

rr 32 of those being duo to lU-nunonia in on epidemic. The G1 pic roraain- _M ._____ . _ H A ^ m #4 ^ a I- 1* . 1. . m 4* ----- --. __ . _- _ ^ 4 a Ah j"4 ab ^ 4 tn ^ Ah a ^ n ^ a aI ft wt 4 n iw m A A 1 ft t Aft. a A For the flrot year of exposure practically the only reaction to the dust wan the pronoueo of scattered phagocytos and an occasional minute asbea- toais body. At 16 and 20 raontha no {prosa response was vieiblo pon the tissue coction but microocopicnlly peribronchiolar foci of inflammatory cells could bo seen. At 24 months (fig. 10) there wan still no change large enough to he eoen with a hand Ions although microscopic 2?r tion revealed cellular accumulations about terminal bronchioles and many more anbestoois bodies, chiefly "within oollo. . The ^lunga of animals ex posed for tho full dusting period of 23 months and afterwards living in normal air tho findings wore similar but at 12 months 3 of 4 anlmalc showed grooaly-vloible charaotoriotic poribronchiolar fibronio "vrith adonomatold chango (fig.'ll). The tracheobronchial nodoe were essentially negative until expoouro had been oontlnuod for more than a year and a half. Animals oacrlficed at 12 months and at 16 months revealed a few minute collections of phap -- cytos containing partiolos but praotioally no fibers lsrgo enoughc to be rocognlted eo ruch. After 20 months of exposure many monocyton witji yellcvr granules were prosent. At 30 months thoro had been increase in rotlaulum but no fibrosis. Wo further changes occurred in tho nodes. Asboatosia bodiea wero not seen in the nodes of any of the guinoa pigs. -25-