It is the purpose of this paper to describe and illustrate how alterations in the fertility and position of the primary and secondary epiphyses may affect the shape and length of the upper end of the femur. It is suggested that under normal conditions of growth two processes are involved: firstly, ossification of parts of the cartilaginous anlage ; and secondly, growth of the whole. Ossification takes place in each area in which a blood supply is present : namely, 1) in the shaJt-periosteal arteries and nutrient artery ; 2) in the nietaphysis-nutrient arteries ; and 3) in the epiphysis-epiphysial arteries. The shaft with its double blood supply is ossified long before the epiphysis. Growth of the whole-Growth in length takes place at both ends of the bone in the area known as the epiphysial plate. Growth in width follows the increase in diameter of the epiphysis.