380 METAPHYSICAL EVOLUTIOK 



Another pair of antitlietic qualities are intensity of action and 

 the reverse. This probably means that a given bulk of brain 

 tissue produces (i. e. , converts) a greater amount of energy in a 

 given time than an equal bulk of non-intense tissue. 



The speed or rate of action in time, and its opposite, slowness, 

 are related to the last-named qualities, but are not identical with 

 them. Thus growth of the mind always witnesses a diminution 

 in the rate of action, but an increase in intensity. 



Tenacity of mental action is a very marked character, and of 

 great importance. It signifies the persistence of mental action, 

 or mental endurance, and may characterize the entire mind, or 

 only a part of it. Its opposite, seen in changeability, desultori- 

 ness or fickleness, may also characterize all or a part only of the 

 mind. According as it characterizes the intellectual or emotional 

 departments are its exhibitions most varied, though they probably 

 have a common histological basis. 



Impressihility and stolidity express antitheses of character 

 which are seen every day. The term impressibility is used as 

 identical with irritability, and is preferred, because the latter has 

 special physiological and popular meanings, some of which are 

 only among its phases. These qualities are apt to pervade the 

 entire mental organism, although, like others, they may char- 

 acterize a part only. Impressibility is obviously a condition of 

 tissue, since it varies greatly with physiological conditions in the 

 same person. Its exhibitions in the department of the emotions 

 may be confounded with strong development of the emotions 

 themselves. A moment's thought, however, shows that easy ex- 

 citation of emotion is a different thing from energy of emotion, 

 and is often found apart from it. Impressibility of intellect 

 shares with tenacity a leading position as an attribute of a first- 

 class mind, and the combination of the two forms a partnership) 

 of superior excellence. 



I may mention here a quality whose absence is pathological, 

 and hence does not properly enter the field ; this is tonicity. In 

 its normal condition, every organ should be supplied with suffi- 

 cient nutriment or energy to insure the occupation of its entire 

 mechanism. Anything short of this is followed by poor work. 

 Debility of mental action in the emotional department is seen in 

 abnormal irritability, such as peevishness or *^ spooning" ; and in 

 the intelligence, in absence of mind and blundering; and in both, 

 in general frivolity. 



