The tenacity of an individual's life, Dr. Powell determined by the following scale of measurements: three-fourths of an inch from the orifice of the ear to the life-line, is the average length in the adult, and indicates _ordinary_ tenacity of life. As the distance decreases to five-eighths, one-half, or three-eighths of an inch, vital tenacity diminishes. If the distance is more than three-quarters of an inch, it denotes great vital endurance, excellent recuperative powers, and is indicative of longevity. If it measures less than half an inch, it shows that the constitution has a feeble, uncertain hold upon life, and an acute disease is very likely to sunder the vital relations. Dr. Powell contended that "life force and vital force are not equivalent terms, because much more vital force is expended upon our relations, than upon our organization in the preservation of life. Every muscular contraction, every thought, and every emotion requires an expenditure of vital force." He asserted that we _inherit_ our life force or constitutional power, and that we can determine by this _life-line,_ the amount which we so receive. And he believed that it could be increased by _intellectual_ effort, just as we can increase vital force by _physical_ exercise. Fig. 89 represents the skull of a man who died, at nearly the same age as Loper, of consumption, in the Charity Hospital, at New Orleans. The measurement of the skull in this case gives a space between the life-line and the orifice of the ear of one-sixteenth of an inch, showing that the consumptive had lived the full term of his life. Dr. Powell contended that the depth of a man's brain may be increased after maturity; muscular effort, mental activity, and a sense of responsibility being favorable to longevity, while idleness and dissipation are adverse to it. In justice to the Doctor, we have stated fully his theory and his method of determining the hardihood and endurance of the constitution, and we bespeak for it a candid examination. Without doubt it embodies a great deal of truth. Hereafter we shall endeavor to indicate by cerebral configuration, a better system of judging of the vital tenacity, hardihood, and constitutional energies, both inherited and acquired. THE VOLITIVE TEMPERAMENT.