Observations on the development of the connective tissues of developing human nerve

Trochlear nerves from two human fetuses, and digital nerves from a third, have been examined by electron microscopy. Very marked differences in maturation were found between trochlear nerves of fetuses of ages differing only by 2--3 weeks, and between proximal and distal parts of the same trochlear nerve. Immaturity was reflected in paucity of endoneurial space and collagen and in the rarity, or virtual absence, of endoneurial fibroblasts. Circumstantial evidence of collagen formation by Schwann cells has been presented and discussed.