Weak stimuli excite physiological activity: Moderately strong stimuli favor physiological activity; Strong stimuli retard physiological activity and very strong stimuli stops physiological activity.

This law explains why severe injuries, in the initial few minutes aren’t as painful. An analogy of this would be when the caveman had to run for his cave when the lion ripped his arm off – this physiologic law explains why there was a brief period of vasoconstriction and decreased pain.