We remarked in our treatment of the simple emotional elements, that pleasure and pain can in no case be estimated by any absolute measure. Now that we have to find some explanation of the delight in pain, which applies to purely physical as well as to mental pain, we begin by admitting that the relative character of feeling probably accounts for many instances in which the pain is merely apparent. The same external stimulus which acts on one individual with hypernormal strength, and therefore evokes pain, may in the case of another individual who has duller senses, produce a weaker impression, and thus call forth a pleasurable reaction. The taste and smell anomalies of hysterical patients afford us good examples of such abnormal pleasure. And, on the other hand, there are plenty of instances, too familiar to be enumerated, in which an impression which a sick person would call painful brings pleasure to a healthy one. Again, the power of receiving pleasurable sensations from strong stimuli may often be increased by exercise. Mr. Marshall has applied his psycho-physiological principles to the interpretation of these “acquired pleasure-gettings” and though he perhaps does not exhaustively and convincingly explain the process, he at least gives a graphic and clear account of its most probable course. He thinks that a hypernormal stimulus indirectly increases the blood-supply to the stimulated organ. This organ will therefore, if the operation of the stimulus is not too prolonged, store up some portion of unused nutritive force during the subsequent repose. And thus, if the same stimulus is shortly afterwards repeated, the organ will be able to respond with greater facility and intensity, _i.e._ react under the conditions of pleasurable reaction. In this way Marshall accounts for the classic instances of acquired liking for olives and tobacco.[78] It is probable that a similar influence of repeated exercise may also operate in the department of compound emotions. Lehmann, who explains the transformation of originally painful impressions into pleasurable ones in a somewhat different way, viz. by his law of “the indispensability of accustomed things” refers to this law those instances in which persons who have had many troubles grow so accustomed to them, that in a moment of ease they feel a kind of loss.[79] The validity of this law will be recognised by every one who has any opportunity of observing the vaguely and weakly unpleasant feeling which sometimes appears when we are suddenly liberated from some pursuing anxiety. And the indispensability of accustomed sensations may impel persons to create new mental pains or worries to replace the old ones.