This phenomenon occurs not alone on the physical plane; it is discernible in mental exertion as well. True, we seldom experience it because we are mentally lazy and have the habit of stopping our work at the first signs of fatigue. Did we persist, however, disregarding fatigue and ennui, we should find ourselves tapping vast reserves of mental power and accomplishing mental feats of astonishing brilliancy. The occasional occurrence of the phenomenon of second-wind gives ground for the statement that we possess more energy than we ordinarily use. There are several lines of evidence for this statement. One is to be found in the energizing effects of emotional excitement. Under the impetus of anger, a man shows far greater strength than he ordinarily uses. Similarly, a mother manifests the strength of a tigress when her young is endangered. A second line of evidence is furnished by the effect of stimulants. Alcohol brings to the fore surprising reserves of physical and psychic energy. Lastly, we have innumerable instances of accession of strength under the stimulus of an idea. Under the domination of an all-absorbing idea, one performs feats of extraordinary strength, utilizing stores of energy otherwise out of reach. We have only to read of the heroic achievements of little Joan of Arc for an example of such manifestation of reserve power. When we examine this accession of energy we find it to be describable in several ways--physiologically, neurologically and psychologically. The physiological effects consist in a heightening of the bodily functions in general. The muscles become more ready to act, the circulation is accelerated, the breathing more rapid. Curious things take place in various glands throughout the body. One, the adrenal gland, has been the object of special study and has been shown, upon the arousal of these reserves of energy, to produce a secretion of the utmost importance in providing for sudden emergencies. This little gland is located above the kidney, and is aroused to intense activity at times, pouring out into the blood a fluid that goes all over the body. Some of its effects are to furnish the blood with chemicals that act as fuel to the muscles, assisting them to contract more vigorously, to make the lungs more active in introducing oxygen into the system, to make the heart more active in distributing the blood throughout the body. Such glandular activity is an important physiological condition of these higher levels of energy. In neurological terms, the increase in energy consists in the flow of more nervous energy into the brain, particularly into those areas where it is needed for certain kinds of controlled thought and action. An abundance of nervous energy is very advantageous, for, as has been intimated in a former chapter, nervous energy is diffused and spread over all the pathways that are easily permeable to its distribution. This results in the use of considerable