On the instability of a cortical point

Slight and transient differences in the depth of narcosis, in the freedom of blood supply, and in the temperature of the preparation modify reactions obtained from stimulation of the motor area in the cortex cerebri with a facility and to a degree not met in the study of purely spinal or decerebrate reflexes. The observer, when first attempting to decipher the rules exhibited by the reflex activities of a spinal or of a decerebrate preparation, naturally turns first to those results which lend themselves best, by regularity and harmony, to exact formulation. Occasional exceptions as they arise are reserved for examination in the future. In a similar manner, the codification of those responses which are obtained with the greatest reliability from the several cortical points is what at first chiefly concerns the observer in the study of the elicitation of different movements from different points in the cortex cerebri.