1883.] Evolutionary Significance of Human Character. 909 
Another pair of antithetic qualities are intensity of action and 
the reverse. This probably means that a given bulk of brain 
tissue produces a greater amount of energy ina 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, desultoriness or 
fickleness, may also characterize all or a part only of the mind. 
According as it characterizes the intellectual or emotional depart- 
ments, are its exhibitions most varied, though they probably have 
a common histological basis. 
Impressibility 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 characterize 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 con- 
founded with strong development of the emotions themselves. 
A moment’s thought, however, shows that easy excitation 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 com- 
bination 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 ensure 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, 
