Date of Award
Life & Environmental Sciences
The discovery of the fourth vitamin, vitamin D has been of the greatest importance to the medical profession as well as to mankind, because it has brought about the solution of the century-old problem of the cause and prevention of rickets. Today, because of this discovery, severe rickets, in civilized countries at least, is coming to be a rare disease.
The search for the antirachitic vitamin makes one of the most interesting stories of modem biological science. As early as 1890 Palm suggested that sunlight possessed an antirachitic action, and in 1919 Hulchinsky successfully employed the ultra-violet rays from a mercury vapor lamp for the cure of rickets. Hess and Unger, in 1921, demonstrated that sunlight had the same effect.
To the English physiologist, Mellanby, though, belongs the credit of the discovery of the specific antirachitic faotcr or vitamin. His reports, published in 1918 and 1919, contain the first accounts of the undoubted production of true rickets in an experimental animal - in this case the dog - and of its cure by dietary means.
On diets consisting chiefly of cereal and small quantities of whole or skim milk, diets which are now recognized as deficient in vitamin D and also in olaoium, there developed in Mellanby’s puppies soft bones, bowed legs and other typical rachitic deformities. More definite proof of the presence of true rickets was obtained from roentgenograms and from chemical analysis of the dog's bones, which were found to have a decidedly low calcium content. When a few cubic centimeters of cod liver oil was added to the diet, rickets failed to appear. Comparatively large amount of butter fat and suet had some effect in the prevention of rickets also, but lard, cottonseed, olive and linseed oils proved entirely ineffective. Here, then, was proof that the cause of rickets was to be found in a definite deficiency in the diet and that the cure lay in the addition of certain specific foods to the ration.3
Drynan, John, "The Sunshine Vitamin" (1958). Life and Environmental Sciences Undergraduate Theses. 553.