Persistence, or Limitation of Force, as applied to the human body and
the human mind. We cannot create force anywhere; we merely appropriate
existing force. The heat of our fires has been derived from the solar
fire. We cannot lift a weight in the hand without the combustion of a
certain amount of food; we cannot think a thought without a similar
demand; and the force that goes in one way is unavailable in any other
way. While we are expending ourselves largely in any single function--in
muscular exercise, in digestion, in thought and feeling, the remaining
functions must continue for the time in comparative abeyance. Now, the
maintenance of a high strain of elated feeling, unquestionably costs a
great deal to the forces of the system. All the facts confirm this high
estimate. An unusually copious supply of arterial blood to the brain is
an indispensable requisite, even although other organs should be
partially starved, and consequently be left in a weak condition, or else
deteriorate before their time. To support the excessive demand of power
for one object, less must be exacted from other functions. Hard bodily
labour and severe mental application sap the very foundations of
buoyancy; they may not entail much positive suffering, but they are
scarcely compatible with exuberant spirits. There may be exceptional
individuals whose _total_ of power is a very large figure, who can bear
more work, endure more privation, and yet display more buoyancy, without
shortened life, than the average human being. Hardly any man can attain
commanding greatness without being constituted larger than his fellows
in the sum of human vitality. But until this is proved to be the fact
in any given instance, we are safe in presuming that extraordinary
endowment in one thing implies deficiency in other things. More
especially must we conclude, provisionally at least, that a buoyant,
hopeful, elated temperament lacks some other virtues, aptitudes, or
powers, such as are seen flourishing in the men whose temperament is
sombre, inclining to despondency. Most commonly the contradictory demand