When we turn to those internal organs of the body which normally carry on their functions in a constant and equable manner, seldom or never obtruding themselves into the sphere of consciousness, any disturbance of function seems much less likely to be translated into dream consciousness in a simple and direct form. It is sufficient to take the example of the heart. When the heart is acting normally any consciousness of its action is as rare asleep as awake. Even when cardiac action is disturbed, either by disease or by temporary excitement, dream consciousness seldom realises the physical cause of the disturbance. Occasionally, indeed, the cardiac disturbance may reach sleeping consciousness without any very remote transformation; thus a lady dreams that she is fainting while really breathing in a slightly laboured and spasmodic way; but at another period the same lady, at a time when she was suffering from some degree of heart weakness, dreamed one night, when the trouble was specially marked, that she was driving sweating horses up a steep hill, urging them on with the whip in order to avoid an express train which she imagined was behind her. This dream of sweating and panting horses climbing a hill has been noted by various observers to occur in connection with heart trouble.[72] The real difficulty of the panting and struggling heart instinctively finds its apparent explanation in a familiar spectacle of daily life. In another case a dreamer awoke from a disturbed sleep associated with indigestion, having the impression that burglars were tramping upstairs, but immediately realised that the tramp of the burglars' feet was really the beating of her own heart. Somewhat similarly, when suffering from headache, I have dreamed of hammering nails into a floor, a theory obviously invented to account for the thump of throbbing arteries.