Mid-sagittal, histological sections, double-stained with Alcian blue (glycosaminoglycans) and picrosirius red (collagen), from normal and MPS I dogs aged 3, 6 and 12 months (A, B, E, F, I and G), with microCT reconstructions of the same samples (C, D, G, H, K and L). MPS I samples appear smaller and narrower, and had irregular surface morphology at 6 and 12 months-of-age. Decreased cartilage on the ventral articulating surface (arrows) was also evident at these ages for MPS I samples. At 3 months-of-age, delayed calcification was apparent towards the tip of the MPS I samples. For all images, ventral (anterior) is towards the bottom and caudal (posterior) is towards the right. Dashed lines indicate approximate location of vertebral body attachment. All scale bars = 2 mm.