[Bain's footnote 31: There is more than association in the case here supposed. Fear, anxiety, and painful emotions generally, cause disorder in the digestive and other vital functions, as a part of their nature. Every mental state can be proved to have its counterpart physical state; joy, sorrow, fear, are each embodied in a distinct group of physical effects in the nervous system, the muscular movements, and the organic processes. The physical side of agreeable emotions, as a rule, is a heightened tone of the purely animal functions. The physical side of fear is a complicated series of effects, one of them being the depression of the organic processes, digestion among the rest. In this respect, however, it more or less resembles severe pain, sorrow, shame, remorse, and other states, characterised by the general phrase "depressing passions;" the depression being both mental and physical.
The reciprocal agency described in the text, whereby the painful sensations of indigestion induce fear, is not dependent on the association of ideas, but on the deep connections of the emotional states with one another, through their physical accompaniments. A painful feeling of indigestion has much in common with states of depression due to mental causes, as, for example, the shock of a misfortune, fear, sorrow, and the like. From this alliance it favours the ideas of depressing states. It does more; it directly reduces that vigorous tone of the system, which is the support of the courageous and sanguine disposition; and hence, surrenders the mind an easy prey to any chance incentive of alarm or anxiety.--_B._]
[Editor's footnote 32: The law of association laid down in this section ranks among the principal of what may be termed the laws of Obliviscence. It is one of the widest in its action, and most important in its consequences of all the laws of the mind; and the merit of the author, in the large use he makes of it is very great, as, though it is the key that unlocks many of the more mysterious phenomena of the mind, it is among the least familiar of the mental laws, and is not only overlooked by the great majority of psychologists, but some, otherwise of merit, seem unable to see and understand the law after any quantity of explanation.