Hardy, Wolff, and Goodell1 found in extensive studies that the threshold of pain in man was independent of the size of the cutaneous area that was stimulated. Whereas temporal and spatial summation processes have a profound influence on the sensory threshold of touch and temperature sensations, the investigations of Hardy and others showed that the pain threshold was lowered by temporal but not by spatial summation. On the contrary, it is well known that both forms of summation influence the intensity and duration of the reflex reactions resulting from nociceptive stimulation. Since this statement is based largely on spinal reflexes, it appeared desirable to investigate the effect of spatial and temporal summations on cerebral reactions induced by nociceptive stimulation.
Experiments were performed on lightly anesthetized cats prepared under thiopental (Pentothal) and local anesthesia, later supplemented by chondodendron tomentosum extract, purified (Intocostrin). Artificial respiration was used routinely. The