The interval which elapses between tapping a muscle or tendon and the resulting movement of the limb has been estimated by many observers—Burckhardt, Tschirjieu, Waller, Brissaud and Francois Franck, Eulenberg, De Watteville, &c.—but the precise signification of these so-called reflexes is not yet fully understood. What follows is intended to add to our knowledge of this subject.