The depth of the base of the brain is a true index of vital tenacity, or duration of life in any individual. This depth varies in different persons from less than a quarter of an inch up to an inch and a quarter.[2] A full inch in an individual fifty years of age indicates a life of eighty or ninety years. One-half to five-eighths of an inch shows that though the person may live many years, yet he has not the vital power to resist formidable assaults of disease. And those persons whose base of brain presents a depth of less than half an inch, must be exceedingly careful of their health, and may expect to die from the most trivial cause. On the contrary, those with three-fourths of an inch, and above it, will probably survive the most powerful attacks of disease. The base of the brain, being the seat of vitality in all animals, the exact size of it shows the quantum of life possessed by any individual. Hereditary diseases may be excepted, in certain cases.