A similar influence is exercised by age. Although pneumonia is common at all ages, its heaviest death-rate falls at the two extremes, under six years of age and over sixty, with a strong preponderance in the latter. Under five years of age, the mortality may reach twenty to thirty per cent; from five to twenty-five, not more than four to five per cent; from twenty-five to thirty-five, from fifteen to twenty per cent; and so on, increasing gradually with every decade until by sixty years of age the mortality has reached fifty per cent, and from sixty to seventy-five may be expressed in terms of the age of the patient. One consoling feature, however, about it is that its mortality is lowest in the ages at which it is most frequent, namely, from ten to thirty-five years of age. And its frequency diminishes even more rapidly than its fatality increases in later years. So that while it is much more serious in a middle-aged man, he is less liable to develop it than a younger one. Where the mortality from pneumonia is highest, is in the most densely populated wards, especially among negroes and foreigners of the hospital class, in individuals who are victims of chronic alcoholism, and also among those who are for long periods insufficiently nourished. Lastly, it is only within comparatively recent years that we have come clearly to recognize the large role which pneumonia plays in giving the finishing stroke to chronic diseases and degenerative processes. It is, for instance, one of the commonest actual causes of death in Bright's disease, in diabetes, in lingering forms of tuberculosis, and in heart disease; and last of all, in that progressive process of normal degeneration and decay which we term "Old Age." It is one of the most frequent and fatal of what Flexner described a decade ago as "terminal infections." Very few human beings die by a gradual process of decay, still less go to pieces all at once, like the immortal "One-Hoss Shay." Just as soon as the process has progressed far enough to lower the resisting power below a certain level, some acute infection steps in and mercifully ends the scene. This is peculiarly true of pneumonia in old age. To the medical profession to "die of old age" is practically equivalent to dying of pneumonia. The disease is so mild in its symptoms and so rapid in its course that it often utterly escapes recognition as such. The old man complains of a little pain in his chest, a failure of appetite, a sense of weakness and dizziness. He takes to his bed, within forty-eight hours he becomes unconscious, and within twenty-four more he is peacefully breathing his last. After death, two-thirds of the lung will be found consolidated. So mild and rapid and painless is the process that one physician-philosopher actually described pneumonia as "the friend of old age."