Much excellent research has been directed toward the elucidation of the effects of special diets and of vitamins on the calcium and phosphorus metabolism. Morgan and her collaborators1 intended primarily to study pyorrhea, but it was felt that a comprehensive study should take account of the changes in bones, blood and excretions as well as of teeth and gingivae.
The experimental observations were made on young dogs taken at weaning at ages of from 5 to 7 weeks. The dogs were placed on artificial diets made up of isolated foodstuffs and were kept on these diets for periods varying up to ten months. They were kept indoors in small pens, with occasional brief periods of outdoor exercise. Clinical mouth examinations, blood examinations and roentgenograms were made once a month. The weights were recorded weekly. At the end of the observation periods, histologic and chemical examinations were made on some