Mouse lung tissue was taken to prepare collagen by pepsin-acid extraction, salt precipitation, re-solubilization in acetic acid, and dialysis and re-precipitation in neutral phosphate buffer. Collagen was re-solubilized and lyophilized. Electrophoresis in SDS polyacrylamide showed that the collagen was of high purity with typical migration of γ, β(2), α1, and α2 bands.