A Study of Rats on a Normal Diet Irradiated daily by the Mercury Vapour Quartz Lamp or kept in Darkness.

IN the course of a study on the absence of rickets during confinement on a good diet, Mellanby [1921] kept four puppies in small kennels in the dark for a period of thirteen weeks. Their diets consisted of: (a) bread, milk and meat; (b) bread, milk, meat and bone; (c) bread, milk, meat and bone that had been autoclaved at 1200 for 15 minutes. The puppies were ten weeks old at the beginning of the experiment and were killed at the age of 26 weeks. Histologically, no sign of rickets was found. Chemical analysis of the shafts of the femurs gave the following percentages of CaO in the dry bone: