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is unnecessary. Experience has shown that nitrogen must be supplied when work is done, and that the amount must increase with the amount of work done. When no nitrogen is ingested the body uses some of its own nitrogen, and becomes fatigued after a small amount of work is performed.

Diet for Old Age.-König gives the minimum diet for an old man as follows: Proteids, 100 grams; fats, 68 grams; and carbohydrates, 350 grams. For an old woman he gives the following amounts: Proteids, 80 grams; fats, 50 grams; and carbohydrates, 260 grams. The food of the aged should be easily digested. With decreased physical energy the digestive powers are also lowered, and hence the nature of the food has to be regulated. Over-indulgence is especially to be avoided. in the aged. Milk, grains, and fruit are well adapted for aged persons.

In an article on "Vegetarianism," A. Schoenstadt1 states that: "There are two parties among vegetarians— the one excludes all animal nutritive materials of whatever nature, and the radical adherents live on only a few vegetables, namely, cereals, fruit, baked food, and water. The other party uses, besides vegetable food, also animal food materials which are obtained without killing the animals, as eggs, milk, cheese, butter, honey. This is really not vegetarianism, but a mixed diet."

Schoenstadt believes that it is possible to subsist on a purely vegetable diet, but states that it is not sufficient nor natural for man. He is of opinion that there is great danger connected with a vegetable diet:

a. Because the nutritive materials supplied are insufficient to meet the requirements of the organism.

b. Because this diet leads to grave digestive disturbances.

He regards this diet as insufficient for the inmates of institutions and prisons.

Influence of Insufficient Food.-Deficiency in proteid 1 Deutsch. Vierteljahr. f. oeffentl. Gesundheitspflege, Bk. xxxii., S. 597.

materials in the dietary is attended with lessened activity and a general lowering of the vitality of the body. This adynamic condition favors the contraction of specific diseases. The omission of fats from the dietary results in illness in a few days. The body is unable to make up its carbon deficit from the other food-substances. Starch can be omitted from the dietary for a long time without detriment if fat is given. Deficiency in salts in the dietary is attended by malnutrition and a disorganized condition of the blood.

A form of deficient nutrition which was formerly quite common, and is still seen at times, is known as scurvy. This condition is brought about by a deficiency of fresh vegetables and fresh fruits, and sometimes to deficiency in fresh meats. It appears to be due to the absence from the dietary of certain organic acids and their salts.

Influence of Excessive Amounts of Food.-When much larger amounts of food are taken than can be utilized by the body the effects are manifested in dyspepsia, diarrhea, and gastro-intestinal irritation. Gout is a condition of the system in which the function of the liver and kidneys is disturbed because of long-continued efforts at eliminating excessive amounts of proteid materials ingested into the system. Excessive amounts of proteid material with deficient fat lead to wasting of the bodyfat. Excessive amounts of fat and starch in the food lead to corpulency and disordered function of the digestive organs.

Nutritional Diseases.-Several diseases are now demonstrated to be due to faulty nutrition, though formerly one of these diseases was regarded as highly infectiousnamely, beriberi. Even to-day the quarantine regulations adopted by the Pennsylvania Quarantine Board for the port of Philadelphia include beriberi among the quarantinable diseases.

Scurvy. For a long time scurvy was a scourge on land and sea, but since the demonstration by Captain Cook in his voyage around the world that this disease could be pre

vented by including lemons in the dietary of sailors, we have learned that the disease can be prevented by limiting the quantity of salted meats in the dietary and adding fresh vegetables and fruits, or even citric acid and vinegar. Scurvy is to-day a rare disease among civilized people.

Beriberi.-The disease develops because of the absence. from the diet of some substance or substances necessary for the normal nutritive processes of the body, most commonly a diet consisting largely of polished rice. Strong and Crowell have shown that the disease may occur in man under the most favorable hygienic conditions, with exception in regard to diet. Beriberi in man may be caused by limited diets which do not include polished rice, according to the observations of Alex Holst on the occurrence of the disease on Norwegian ships; of Little 3 on the existence of beriberi on the coasts of Labrador and Newfoundland, where white wheat flour is the chief article of diet in certain seasons; and of Lovelace as to the occurrence of cases in Brazil.

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The observations of Fletcher and Fraser and Stanton " have shown that diets consisting chiefly of polished rice are the common cause of beriberi in the Orient. substitution of unpolished rice for polished rice eliminates beriberi. Gibson' found that the addition of calcium lactate to a polished-rice diet served to delay the onset of polyneuritis in fowls. Vedder and Clark found that the addition of peas and peanuts to a polished-rice diet prevented the development of polyneuritis in fowls.

Beriberi was demonstrated by Baron Takaki to be due to the use of diet consisting largely of rice, and that it could be prevented by the addition of small quantities.

1 The Philippine Journal of Science, Sept. 13, 1912, p. 271.

2 Jour of Hygiene, 1907, p. 619.

3 Jour. Am. Med. Assoc., 1912, p. 2029.

Ibid., p. 2134.

Lancet, 1907, p. 1776.

Ibid., 1909, p. 451.

7 Philippine Jour. of Science, Sect. B., 1913, p. 351.

8 Ibid., 1912, p. 423.

of meat and legumes to the dietary. It seems evident from the experimental study of the question that beriberi is caused by a diet deficient in some as yet unknown substance which is contained in the polishings removed in the process of polishing, and that unpolished rice does not cause beriberi.

The nature of the substance removed from rice in the process of polishing has not been determined, but it is of great physiologic importance in the nutrition of the body. This substance is soluble in 0.3 per cent. hydrochloric acid, and is destroyed when heated to 120° C. for one hour. This substance is also soluble in water and in 91 per cent. alcohol.

Pellagra.-Lombroso and his followers have contended for many years that pellagra is due to an intoxication produced by poisons developed in spoiled corn through the action of certain micro-organisms which in themselves are harmless to man. Sambon1 believes that the disease is due to a protozoal organism in all probability distributed by a species of Simulium, the sand fly in Europe. Niles? believes that the evidence in support of Sambon's belief is insufficient, and that the intoxication theory of Lambroso gives the most satisfactory explanation of the cause and character of the disease.

1 Policlinico, Rome, 1910, abstract Jour. Am. Med. Assoc., 55, 1910, 361. 2 Pellagra, W. B. Saunders Co., 1912.

CHAPTER VIII.

EXERCISE.

IN order to maintain a perfect state of health of the body it is essential that each organ has a certain amount of exercise. All the bodily functions are attended with rhythmic motion, and these movements are facilitated by exercise. If there is deficient exercise of a portion of the body, continued for some time, the nutrition of this portion is impaired, the organs or members involved decrease in size and eventually degenerate in structure as well as in function. Overexertion of a portion of the body leads to abnormal nutrition and development of the organs or members involved, and if continued for some time degeneration may occur, which is as great as that resulting from disuse of the organs. It is essential, therefore, that the exercise is as uniform as possible for all the organs and members of the body so as to avoid over- or under-stimulation of any of its parts. Perfect health is dependent upon the uniform stimulation of all the functions, so that all the organs may be in a condition to act in their natural way and normal capacity.

The amount of energy expended in walking on a level is usually assumed to equal that required to lift onetwentieth of the body-weight through the distance walked. The most important effect of muscular exercise of any kind is produced on the lungs and circulation.

Effect on the Lungs.-Smith has found the effect of exercise on the amount of air respired, to vary in direct proportion with the amount of exertion. Taking the recumbent position as unity, he found the amounts of air inspired as follows:

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