The distribution of collagen in human articular cartilage with some of its physiological implications.

1. Serial slices of articular cartilage obtained at necropsy from apparently normal femoral condyles of individuals between the ages of twenty-six and sixty were examined chemically, by electron microscopy and for permeability. 2. The most superficial layer was shown by chemical analysis and electron microscopy to have the highest collagen content, which fell sharply with distance from the articular surface. On the other hand the glycosaminoglycan content was very low in the superficial layers but increased with depth. This variation was found in all specimens tested but the absolute levels of collagen and of glycosaminoglycans were widely different. There was no correlation of chemical composition with age. 3. Collagen fibrils in the superficial layer were of much smaller diameter than in the deeper zones. 4. Hydraulic permeability was shown to depend more on glycosaminoglycan than on collagen content, although it varied inversely with both these factors. 5. The results obtained demonstrate clearly the close relation between the physical properties of cartilage and its chemical composition.