This section is from the book "Health Without Medicine. A Treatise On The Laws Of The Human System", by Larkin B. Coles. Also available from Amazon: Philosophy Of Health.
Human sympathy is a quality of our natures which the Creator has implanted in us; and whoever cultivates and exercises it, yields to a law of his social character -- obeys a law of his nature; and whoever cherishes a due spirit of obedience to any law of his being, is doing that which is promotive of his health. In willing good to others -- which necessarily involves all practicable benefactions -- there is a pleasant sensation passes over the mind, which also vibrates over the whole body; and this heaven-born vibration of human sympathy and goodwill, gives a glow of health to the whole mental and animal system. Hence, the fact, that in times of the prevalence of pestilential diseases, those who devote themselves to the self-sacrificing effort of nursing and watching the sick and dying, while the victims of the malady are fast falling on their right and left, seldom become a prey to that malignant disease themselves. The great philanthropist, John Howard, could never have endured so long his labors amidst the varied death-damps of prisons and dungeons, and appalling scenes of wretchedness to which he exposed himself, had not the desire and the pleasure of doing good, for the sake of humanity and of God, given to his system unwonted power of resistance to disease and endurance of toil.
He who wills good to his fellow-beings, and. so far as able, gives practical demonstration of his benevolence, is not only relieving the ills of human life in others, but is at the same time contributing largely to his own health of soul and body. The Great Teacher of practical benevolence fully appreciated the personal benefit to be derived from the exercise of a spirit of benevolence, when he said, "It is more blessed to give than to receive." Let those who have never made the experiment, begin at once to yield obedience to this law of their social being, and they will find that in doing so, they will receive their reward.