The purpose of this communication is to analyze the histology of the extra-ocular muscles with special reference to the possibility of ocular proprioceptive sense in man. Many isolated reports on the extraocular muscles have appeared in the literature, but they do not seem previously to have been brought together and correlated.
THE EMBRYOLOGY
First, the embryology of the extra-ocular muscles will be reviewed briefly.1 In the 7 mm. human embryo these muscles are seen as a single, undifferentiated, massed condensation of paraxial mesoderm surrounding the optic vesicle. At this stage the third nerve enters the anterior part of the muscle mass, dorsal to the optic stalk. At 9 mm., the mass is enlarged and begins to split into different muscles, with their respective nerves entering the dividing muscle mass. At 14 mm., all the muscles are formed and in about the same position with respect to the