There is another matter relative to old age and diet which is of vital concern. The rule is that leanness and longevity go together. This is a law of nature to which there are comparatively few exceptions. "The typical man of eighty or ninety years," says Sir Henry Thompson, "still retaining a respectable amount of energy of body and mind, is lean and spare, and lives on slender rations. A man of advanced years who is growing thin has little hope of remedying his leanness by diet or patent preparations.

I count myself qualified to speak from personal experience on this point. Within the past six years physical misfortunes from which there seems to be little hope of a permanent recovery, have reduced my weight from one hundred and fifty-three pounds to one hundred and twenty-five pounds. No part of this loss can be re stored to me by fattening foods or flesh-forming emulsions or tablets. But as I approach threescore and ten, and better comprehend the simple life and what not to eat, and how not to worry, I wouldn't give a nickel a pound for any flesh which, by any artificial means, could be added to my slender body.

Mrs. Ellen Henrietta Richards, instructor in sanitary chemistry in the Massachusetts Institute of Technology, is one of the ablest physiological chemists in this country. In her special line she has done excellent work for the United States Government, and is the author of several works on the subject of foods. When I wrote her for an opinion as to what food was best adapted to persons of advancing years, she said:

"Massachusetts Institute of Technology, "Boston, October 20, 1904.

"My dear Col. Smith:

"There is no such thing as a definite dietary for any ten persons, let alone one thousand. What is one man's meat is another's poison.

"Our only test is in the result, and one may eat food prepared in a certain way with satisfaction, while another will not eat it and will not thrive on it.

"The simplest way is by expulsion of hearty dishes, of hearty meats, and of puddings and pastry, of strong acids like vinegar, of many kinds of food at one meal. See to it that whatever food is used it will be well-cooked and simple, that is not many ingredients in one dish but well flavored; that the quantity is not large at any one meal, and that the meals are frequent if it suits. Ellen H. Richabds."

In regard to the matter of two or three meals a day, Wilbur Olin Atwater, professor of chemistry in Wesleyan University, and special agent in charge of the nutrition investigation made by the Department of Agriculture, Washington, says:

"The best physiological evidence implies that moderate quantities of food taken at moderate intervals, are more easily and completely digested by ordinary people, than larger quantities taken at longer intervals. If the same amount of food is to be eaten it is hard to see the advantage of two hearty meals over three ordinary meals."

To eat rationally and obtain the best results possible from what we eat, it is important that we should understand the classes into which nature has divided the various foods. A simple statement respecting these divisions will no doubt be helpful to practical people who desire to get the most good from the food they use.

There are three principal classes of foods - proteids, carbohydrates, and fats. Proteids - which are also designated as proteinous, albuminous, and nitrogenous foods - include the lean of meats, the white of eggs, nuts, the curd of milk, and the gluten of bread. They are also found in large proportion in fish, game, peas, beans, lentils, and in cereals and a few vegetables.

The proteids are the most important of all food compounds, because they make blood, muscle, nerve, bone, and renew the waste which is continually going on in the body. They possess a function which cannot be performed by any other foods. Only on them can the health, mental and physical vigor be permanently maintained.

It should be borne in mind that the stomach is capable of digesting only meats, and animal foods, such as eggs, milk, and cheese. It has little or no power over the starches, sugar, and fats; and as our daily food is largely composed of the latter class, it is said that the stomach plays only a small part in digestion. And yet it is one of the most abused organs of the body.

Carbohydrates embrace the sugars, the starches found in abundance in bread, potatoes, rice, sago, tapioca, the various cereals, honey, syrups; and in a moderate quantity in fruits and vegetables. These are valuable foods in that they supply the body with heat and energy, and are also transformed into fat While the proteids may furnish a certain amount of heat, the carbohydrates, which are burned in the body, cannot make muscle, bone, nor repair waste tissues. Just as coal generates steam for the locomotive, the carbohydrates produce heat and power for the human body.

It should be understood that all starchy foods are digested by the pancreatic juice and the small intestines; but practically, the digestion begins in the mouth, and for that reason they should be completely masticated. I emphasize this fact because very many of the troubles arising from indigestion are intestinal, and these can be avoided by simply masticating thoroughly all farinaceous or starchy foods, such as rice, potatoes, sago, bread, and so on, and placing an hygienic limit as to their use.

Eats do not make blood, bone, nor muscle, but form fatty tissues and serve to develop some heat the same as starches, and like them and a limited portion of the proteids, they are burned in the body. The fats are digested by the bile, aided to some extent by the pancreatic juice.

To attempt to state definitely what proportion of proteids, fats, and carbohydrates should form a dietary for everybody would be foolish for the reason that a combination of foods that would agree with one person might disagree with another. However, physiologists have ascertained by repeated and thorough experiments that as a rule the food should consist of from fifteen to twenty per cent, of proteids and from sixty to seventy-five per cent, of carbohydrates.