This section is from the book "Meals Medicinal", by W. T. Fernie. Also available from Amazon: Meals Medicinal: With "Herbal Simples" Curative Foods From the Cook in Place of Drugs From the Chemist.
It has been already stated that an infusion of the dried Rosemary plant, (leaves, and flowers), being used when cold, makes one of the best hair-washes known; its volatile oil specially stimulates the hair-bulbs to renewed activity. Physiologists (particularly M. Metchnikoff, of the Pasteur Institute,) now tell us why the hair becomes white as old age supervenes. Its pigment colour lies scattered, during early and middle life, between the two layers of each hair; whilst the hostile cells, or phagocytes, are all the time in subjection, because of the physical strength, and endurance then personally possessed. But in old age these hostile cells, which occupy the hairs' central cylinder, gain the ascendency, and proceed to devour all the pigment within their reach, afterwards ejecting it from the body, and leaving the hair grey, or white. In like manner, as the years approach senility the higher nerve cells of the brain, which subserve intellectuality, sensation, memory, and control of movements, tend to disappear, and are replaced by elements of a lower kind, the superior nervous cells being devoured by these "macrophags".
But the higher cells of the spinal marrow are much less subject to such ravages of senile decay than those of the brain. Nevertheless, in old age generally the dominant cells of the various vital organs suffer gradual inanition, whilst the activity of the consuming phagocytes, or white corpuscles, is enormously increased; they batten, for lack of other food, upon the nobler organs of the human frame. But here steps in the modern physiologist with a new theory, and a saving promise for the future. "In a few years," boasts he, "at the Pasteur Institute, or elsewhere, we shall find out a sustaining serum (or soup,) which will keep these phagocytes still supplied with their necessary nourishment, and will thus prolong the vitality of heart, and brain, and lungs in the human individual. It will then come about that from twenty to twenty-five years a man shall live for himself, and his family; from fifty to a hundred for science, and humanity; and after a hundred for the State. Honoured, useful, in full possession of all his faculties at six score years and ten, the greybeard of the approaching future will be among the most enviable of mankind. We ought to reach one hundred and forty years of age.
A man who expires at seventy, or eighty, is actually cut off prematurely in the flower of his days".