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: Puppy No. 25 ... ... 42-92 26 ... ... 38-13 27 ... ... 37T46 28 ... ... 30*00 These values Mellanby considers to be high.It is evident from the foregoing facts that the calcium content of the bones was unaffected by 13 weeks of confinement in the dark.Raczynsky [1912] investigated the effect of sunlight and darkness on puppies during the period of lactation.He took two puppies from the same litter, born in May, kept one in total darkness from birth and the other in sunlight, both suckled by the same mother.After six weeks they were killed
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Goldblatt et al. (1923) studied this question.