Every human being receives at birth a certain amount of capital in the form of vital force. To judge from the law which apportions to mammalia about the five-fold span of time requisite for the perfect development of the skeleton, normal man—i. e., a human being—born of healthy parents, perfectly healthy himself, and spending his vital force properly and economically, may live, as a rule, from one hundred to one hundred and twenty years, and in exceptional cases may attain the age of one hundred and fifty, and even more.
Most exact observations have proved that the horse, which requires five years before its frame is firmly set, lives to an age of five times five, or twenty-five to thirty years; the camel, requiring «ight years, to an age of five times eight, or forty years; the dog, requiring two years, to twice five, or ten years; the elephant, requiring forty years, to an age of five times forty, or two hundred years. This is the rule. But exceptional horses have lived fifty years, and even longer. There is in the museum at Manchester the skull of a horse that lived more than sixty years. (more…)