To the Editor: —Dr. A. F. Hess, in his Cutter Lecture at Harvard a few weeks ago, remarked that "advance in our knowledge of rachitis promises to be greater during this decade than through the preceding 250 years." He asserts that the dietary deficiencies play a very significant part in the etiology of rachitis. A number of years ago, when I was connected with the West End Children's Hospital and Dispensary, Boston, we were having a large number of rachitic children in our daily clinics, a majority of them from among the colored population. The superintendent, Dr. H. C. Haven, informed me that he had made quite an exhaustive study of rachitis with especial reference to the causes of the disease, and he came to the conclusion at that time that environment, lack of sunlight and fresh air were the probable causes. He stated that among the colored in Africa,