Fig. 4. (A) Low-magnification electron micrograph of lung tissue from Macropus eugenii at birth. Scale bar, 2 µm. (B) Enlargement of the airspace region highlighted in black in A, showing the distribution of SP-D associated with large aggregate extracellular surfactant. Immunogold particles are indicated by arrows. Scale bar, 1 µm. (C) Enlargement of the cell region highlighted in white in A, showing the distribution of SP-D associated with the periphery of the lamellar bodies. Immunogold particles are indicated by arrows. Scale bar, 0.5 µm.