Normal osteoid tissue.

The results of a histological study of normal osteoid tissue in man, the monkey, the dog, and the rat, using thin microtome sections of plastic-embedded undecalcified bone, are described. Osteoid tissue covers the entire bone surface, except for areas of active resorption, although the thickness of the layer of osteoid tissue varies at different sites and in different species of animals. The histological features of osteoid tissue, apart from its amount, are the same in the different species studied. Distinct bands or zones are recognizable in some layers of osteoid tissue, particularly those of greatest thickness, and their significance is discussed. Some of the histological features of the calcification front are described.