1. The numbers of fibres within the peripheral nerves to the hind-limb of Eleutherodactylus martinicensis have been studied during development. The results have been collated with observations on the development of movement in the living embryo.

  2. By the time that the first movements of the limb occur, most of its nerves are recognizable, though the muscles themselves are still in an early stage of differentiation. The numbers of fibres in these nerves is then not greatly different from those which are found at the end of development.

    As the limb movements increase in scope, the numbers of fibres within the larger nerves increase to a maximum.

  3. In the last 2 days of development, when the tail of the embryo is being resorbed, a drastic loss of fibres occurs in the larger nerves, both muscular and cutaneous. This is accompanied by an increase in diameter in some of the remaining fibres.

    The larger muscles of the thigh decrease in volume towards the end of development, at approximately the same time as the number of fibres in the nerves by which they are supplied is reduced.

  4. A hypothesis is suggested of the origin of specific relationships between nerve fibre and end organ by selection.

You do not currently have access to this content.