QUOTE : We have seen that there are two forms of stimulus which are particularly prone to evoke migrainous reactions in predisposed individuals: inordinate excitations or arousals, and inordinate inhibitions or slumps. Within certain “allowable” limits (which vary greatly from person to person), the nervous system maintains itself in a region of equilibrium, homeostatically, by means of continuous, minor, insensible adjustments; beyond these limits, it may be forced to react by sudden, major, symptomatic adjustments.