1. The first foetus described probably represents the early stage of arthrogryposis multiplex congenita. There are two apparent causes of deformity in this condition,—first, muscle imbalance due to unequal maturity of opposing muscle groups: and, second, retained foetal positions as the result of insufficient total muscle volume.
2. The only deformity presented by the second foetus is club-foot, apparently caused by abnormal skeletal-muscle development. The muscle abnormality consists of degenerating muscle fibers which fail to keep paw with skeletal growth, the relative shortening of these fibers being the apparent cause of the deformity.
3. In neither foetus does the club-foot deformity seem to be a retained early foetal position. The skeletal structures of the foot apparently developed normally until displaced by abnormal muscle fotces.
4. The skeletal structures of the club foot show the early stages of medial displacement of the cuboid upon the calcaneus.
5. It is suggested that the skeletal-muscle factor be investigated in congenital posterior angulation of the tibia, and in congenital dislocation of the hip and acetabular dysplasia.