Findlay (2) in a recent historical survey of rickets says: "In this (England) as in most civilized countries, rickets is one of the most common diseases of childhood. Further, it is probably the most potent factor in interfering with the efficiency of the race. It not only stunts the growth and causes deformities, some of which greatly increase the dangers of child-bearing in the female, but it raises considerably the mortality rate of such diseases as measles and whooping cough, and is responsible for the rejection annually of a not inconsiderable number of army recruits."

Schmorl (3) examined hundreds of children and found that 90 per cent of all who died under four years of age had had rickets. Dick (4) reported that 80 per cent of all the children in London County Council Schools had had rickets. Hess and Unger (5) found the disease present in nearly all the negro children in the negro quarter of New York, and they recently state that "all seem to agree that it occurs in more than 50 per cent of the children of the poor." Thompson (6) reports that more than 50 per cent of the children of Edinburgh, London, Glasgow and Manchester suffer from rickets. It will be readily apparent, therefore, that rickets constitutes a national health problem of first importance.

Rickets is a disease which has long afflicted the human race. It was described in its general features by Soranus in the first century of the Christian Era (7). He stated that the majority of Roman children suffered from deformity of the spine and crooked legs, and noted that this abnormality of growth was more common in the neighborhood of Rome than in other places. He said further, that the disease was unknown among the Greeks, and attributed this to the greater interest and care bestowed by the Greek mothers upon their infants, than was customary with the mothers of Rome. Defects of skeletal development of the nature of rickets appear not to have existed in Ancient Egypt.

Rickets as a clinical entity was first described in some detail by Francis Glisson in 1650 (8), and his work has become one of the classics of medical science. He described the enlargements of the ends of the long bones, the deformity of the thorax, the "rosary" due to enlargement of the junctions of the bony ribs with their cartilages, the abnormally large head, the protruding abdomen, the flacidity of the musculature and the generally wasted condition of the body. He pointed out that the disease was not usually fatal, and attributed the deformity to unsym-metrical growth of the two sides of the bones because of interference with the blood supply.