1. The densities of dog bone specimens both when hydrated and dry have been reported. Although a trend toward correlation of these two characteristics appears in the material used, such correlation is not to be expected in all bone specimens.
2. The water content of the bone has been correlated with the density of the hydrated specimen.
3. The dry-substance content of the bone has been correlated with the density of the dry specimen. The mass of the dry Specimen largely represents calcified osteoid. Variations in dry density represent in large part more or less complete calcification of the osteoid.
4. In specimens from normal puppies, those with a very low density when hydrated have a slightly lower density when dry and a slightly smaller ratio of ash + carbon dioxide space to organic component.
5. Variations in these relationships probably exist in bones from animals of different species and in disease states affecting bones of animals of any one species.