This high-power photomicrograph shows an alveolus filled with numerous round bodies up to 25 mm in diameter. Some of these double-contour bodies (1) have a dense center and a clear halo. These are the Blastomyces organisms. The typical B. dermatitides organism is smoothly-outlined with a central, densely basophilic cytoplasm surrounded by a clear halo. When stained with hematoxylin and eosin, the organism is outlined by a relatively thick cell wall. There are also numerous inflammatory cells (2) in the alveolus--neutrophils, lymphocytes and macrophages--which produce a pyogranulomatous inflammatory reaction.