BY HARRY D. PATTON

ONE OF THE MOST EXCITING and fulfilling physiological accomplishments of this century has been the analysis of the spinal reflex system. This triumph has progressed through three major eras. The first, beginning late in the last century and extending into the first decades of this century, was the era of myographic analysis of reflexes; it emanated mainly from Sir Charles Sherrington's laboratory at Oxford and resulted in the award of the Nobel Prize to Sherrington (jointly with E. D. Adrian) in 1932. The final era extended through the 1950s and 1960s and was characterized by the use of micropipette electrodes to measure membrane potentials of motoneurons subjected to controlled afferent inputs. A refinement of this technique utilizes computerized averaging of membrane potential transients that permits one to assess the influence of single filter inputs. Many investigators engaged in this phase of the analysis but the major protagonist of the microelectrical technique was Sir John Eccles for which he received the 1963 Nobel award (with A. Hodgkin and A. F. Huxley). Sandwiched between these two eras was a fertile and productive period in which the fundamental technical approach involved the use of monosynaptically evoked ventral root discharges as measures of the numbers of reflexly discharged motoneurons