Figure 4. Photomicrographs of rat lung tissue stained with H&E (magnification: × [A and B]; ×200 [C and D]; and ×400 [E and F]). In A, C, and E, lung tissue from rats exposed to room air (control group). In B, D, and F, lung tissue from rats exposed to mainstream cigarette smoke. Double arrows indicate merged alveoli resulting in airspace enlargement. Scale bars: 20 µm.
