“If we ask how we must live to secure the best health and longest life, the answer must be drawn from physiological knowledge; but if we ask how long the best mode of living will preserve life, the reply is, Physiology cannot teach you that. Probably each aged individual has a mixture of good and bad habits, and has lived in a mixture of favourable and unfavourable circumstances. Notwithstanding apparent diversity, there is a pretty equal amount of what is salutary in the habits and circumstances of each. Some have been ‘correct’ in one thing, some in another. All that is proved by instances of longevity in connexion with bad habits is, that such individuals are able to resist causes that have, in the same time, sent thousands of their fellow-beings to an untimely grave; and, under a proper regimen, they would have sustained life, perhaps, a hundred and fifty years.
“Some have more constitutional [or inherited] powers to resist the causes of disease than others, and, therefore, what will destroy the life of one may be borne by another a long time without any manifestations of immediate injury. There are, also, constitutional peculiarities, but these are far more rare than is generally supposed. Indeed, such may, in almost every case, be overcome by a correct regimen. So far as the general laws of life and the application of general principles of regimen are considered, the human constitution is one: there are no constitutional differences which will not yield to a correct regimen, and thus improve the individual. Consequently, what is best for one is best for all.... Some are born without any tendency to disease while others have the predisposition to particular diseases of some kind. But differences result from causes which man has the power to control, and it is certain that all can be removed by conformity to the laws of life for generations, and that the human species can be brought to as great uniformity, as to health and life, as the lower animals.”
With Hufeland, Flourens, and other scientific authorities, he maintains that:—
“Physiological science affords no evidence that the human constitution is not capable of gradually returning to the primitive longevity of the species. The highest interests of our nature require that youthfulness should be prolonged. And it is as capable of being preserved as life itself, both depending on the same conditions. If there ever was a state of the human constitution which enabled it to sustain life [much beyond the present period], that state involved a harmony of relative conditions. The vital processes were less rapid and more complete than at present, development was slower, organisation more perfect, childhood protracted, and the change from youth to manhood took place at a greater remove from birth. Hence, if we now aim at long life, we can secure our object only by conformity to those laws by which youthfulness is prolonged.”
As for the omnivorousness of the human animal:—
The ourang-outang, on being domesticated, readily learns to eat animal food. But if this proves that animal to be omnivorous, then the Horse, Cow, Sheep, and others are all omnivorous, for everyone of them is easily trained to eat animal food. Horses have frequently been trained to eat animal food,[267] and Sheep have been so accustomed to it as to refuse grass. All carnivorous animals can be trained to a vegetable diet, and brought to subsist upon it, with less inconvenience and deterioration than herbivorous or frugivorous animals can be brought to live on animal food. Comparative anatomy, therefore, proves that Man is naturally a frugivorous animal, formed to subsist upon fruits, seeds, and farinaceous vegetables.[268]
The stimulating, or alcoholic, property of flesh produces the delusion that it is, therefore, the most nourishing:—
“Yet by so much as the stimulation exceeds that which is necessary for the performance of the functions of the organs, the more does the expenditure of vital powers exceed the renovating economy; and the exhaustion which succeeds is commensurate with the excess. Hence, though food which contains the greatest proportion of stimulating power causes a feeling of the greatest strength, it also produces the greatest exhaustion, which is commensurately importunate for relief; and, as the same food affords such by supplying the requisite stimulation, their feelings lead the consumers to believe that it is most strengthening.... Those substances, the stimulating power of which is barely sufficient to excite the digestive organs in the appropriation of nourishment, are most conducive to vital welfare, causing all the processes to be most perfectly performed, without any unnecessary expenditure, thus contributing to health and longevity.
“Flesh-meats average about thirty-five per cent of nutritious matter, while rice, wheat, and several kinds of pulse (such as lentils, peas, and beans), afford from eighty to ninety-five per cent; potatoes afford twenty-five per cent of nutritious matter. So that one pound of rice contains more nutritious matter than two pounds and a half of flesh meat; three pounds of whole meal bread contain more than six pounds of flesh, and three pounds of potatoes more than two pounds of flesh.”