a more liberal supply of proteids. (7) By temperature and climate. The influence of low temperatures results in increased oxidation of carbon, hence an instinctive craving for more fatty food and the carbohydrates, sugar and starches during the winter months and in cold climates. In the summer months and in warm climates there is a repugnance for fat and a craving for refreshing food and drinks, and hence the minimum amount of fat, about 40 grams and between 300 to 400 grams of carbohydrates with a normal protein ration will meet the requirements. Food stuffs are classified according to their proximate composition as follows: First: Organic, nitrogenous, as proteids or albuminoids; non-nitrogenous—a. fats, b. carbohydrates, c. vegetable acids. Second: Inorganic-mineral salts and water. Third: Food accessories, as tea, coffee and condiments. The first two classes of food stuff are essential to life, the third class is important as favoring palatability and digestibility. The true nutrients are protein, fats and carbohydrates. The term "protein" includes most of the nitrogenous food compounds, such as albuminoids, gelatinoids and extractives. 1. The albuminoids include all substances allied in their chemical composition to egg albumin, and have an average composition of N. 16%, C. 53%, H. 7%, O. 23%, S. 1%. They are found in eggs, lean part of meat, milk, curds and the gluten of wheat, the leguminous plants, etc. The principles of this group during digestion with the exception of nuclein are converted into soluble peptones or alkaline albuminates and readily absorbed as such; they are the chief tissue formers of the muscles and tendons of the body, but apart from this purely plastic function, they also play a role in oxidation and therefore in the generation of heat and energy. At all events they can take the place of fats and carbohydrates if the body has not enough of one or the other for fuel, but neither of the latter can take the place of albuminoids in building and repairing tissue. 2. The gelatinoids resemble the albuminoid group in their chemical composition; they are derived from ossein and chondrin (connective tissue) and are changed to gelatin on heating with water, and during digestion into gelatin-peptones. They are not tissue formers, but serve as fuel, and thus protect the protein fats and carbohydrates from consumption. Indeed 100 grams of gelatin can take the place of 36 grams of albumin and 25 grams of fat, but unfortunately large quantities are liable to cause nausea and diarrhea, probably because the undigested particles undergo rapid decomposition. 3. The extractives, so called because they are extracted from flesh by water, are known in the laboratory as creatin, creatinin, carnin, etc., and are the chief constituents of beef-tea and meat-extracts. Neither the extractives or amids found in vegetables like asparagus, betain, etc., can replace or exert a sparing effect on the consumption of albumin; they are therefore alimentary aids and not true foods. Indeed Kemmerich, over twenty years ago, pointed out that they are not free from danger on account of the large percentage of potassium salt; at all events, it has been shown that animals fed exclusively on meat extracts die more quickly from starvation than do those deprived entirely of food, and Fothergill, one of the most distinguished English foodexperts, expressed the opinion "that more lives have been lost by a mistaken belief in the food-value of beef-tea than by all the Napoleonic wars." Beef-tea acts as a regulator and stimulant of digestion and assimilation and like the meat-broths is useful in the dietary of sickness, provided we combine it with eggs, farinaceous food and small quantities of gelatin. The meat peptones and fluid meat, containing, as they do, considerable proportions of true nutriments, are much to be preferred but their nutritive value in the treatment of disease must not be overestimated. 4. The hydrocarbons of fats, whether derived from the animal or vegetable kingdom, are emulsified and saponified by the pancreatic juice and bile and finally reach the tissues where they become an integral part of the cells. Apart from aiding in the reconstruction of fatty tissues they undergo oxidation and thus supply heat and energy. Since the cells without exception contain more or less fat, it being, in conjunction with albumin, the principal constituent of nerve tissue, a store of adipose tissue, especially during febrile conditions, hard work or whenever the consumption exceeds the supply is very desirable. If the supply of fat exceeds the demand the excess is eliminated in the feces while other portions are stored up in the visceral cavities and subcutaneous tissues, where it serves as a non-conductor of heat, gives beauty and form to the body and protects various important structures from injury, but most important of all, if the supply should be cut off, or the consumption be increased, as during febrile conditions and hard work, this reserve fuel can be drawn upon for the production of heat and energy and thus protect the more important protein-compounds from oxidation. 5. The carbohydrates are non-nitrogenized principles which, in addition to carbon, contain hydrogen and oxygen in the proportion to form water. The formula for starch or dextrose is C.HO, and that of sucrose or cane sugar C12H22O11 The carbohydrates, whatever their source, enter the blood as sugar; normal blood contains about 0.1% and rarely more than 0.2% of sugar. The liver prevents a large accumulation by storing it up as glycogen or liver-starch, which under the influence of a peculiar ferment is re-converted into sugar as the needs of the economy demand, and any further excess is removed by the kidneys. The sugar in the blood is carried to the tissues, where it undergoes oxidation, yielding heat and energy. It is generally held that carbohydrates when ingested in liberal amounts may be converted into fat. How this is accomplished is not yet understood, but it may partly be accounted for by the fact that the oxidation of sugar saves the fatty and protein tissues from destruction and allows the fat in the diet to form new fatty tissues. 6. The pectin substances, like pectose and pectin, found in fruit and tubers, form jellies with water, are related to the carbohydrates and probably serve similar purposes in the economy. 7. The organic acids, like tartaric, mallic, citric, acetic, oxalic and lactic acids existing in fresh vegetables and fruits, fresh meats and milk, are transformed in the system into carbonates and as such preserve the alkalinity of the blood and other fluids. In the absence of these acids the blood becomes impoverished and scurvy is liable to develop. An excess is likely to interfere with digestion, especially with the conversion of starch into sugar, not to mention the laxative and diuretic properties. 8. The fact that 60% of the body is composed of water clearly indicates that a sufficient amount must be introduced to make up the loss sustained by its excretion through the lungs, kidneys, skin and feces. It is simply necessary to recall the physiological functions of water in the absorption and assimilation of food, the elimination of waste products, and its role as a heat regulator to appreciate that a deficiency is certain to be followed by injurious effects. 9. The mineral salts, which furnish about 6% of the body weight, are potassium, calcium, magnesium, sodium and iron in combination with chlorine, phosphoric, sulphuric and carbonic acid. The phosphates of lime, potash and magnesia contribute largely to the formation of bone, and are also essential for the growth of the nervous system. Iron is required for the red blood corpuscles and coloring matters, the chlorides are the source of hydrochloric acid in the gastric juice and keep the globulins of the blood and other fluids of the body in solution. Potassium for the blood cells and solid tissues and sodium for the intercellular fluids are all essential for the growth and repair of the tissues; of these certain quantities are daily eliminated and must be replaced. Forster has shown that when the supply in animals is suspended, serious digestive derange ments, depression of the nervous system, muscular weakness, trembling, paralysis, stupor and death ensue. Voit's experiments indicate that an insufficient supply of the salts of lime produced rickets in growing animals, and children fed largely upon farinaceous food are proverbially prone to this affection; incomplete absorption of these salts produces the same effect, as shown by the frequent development of rickets after prolonged diarrheal affections. An insufficient supply of iron or incomplete absorption may give rise to chlorosis and anemia, and a deficiency of the potassium salts in consequence of an exclusive animal diet is believed to favor the development of scurvy, but as this disease has developed among prisoners who subsisted largely on a vegetable diet, I quite agree with Fluegge that the absence of fresh vegetables, more especially the organic acids contained therein, is the most important factor in the development of scurvy. An excess of chloride of sodium, as during a constant salt meat diet, doubtless predisposes to scurvy, probably because the chloride of sodium exerts a decomposing effect on the potassium combinations of the blood corpuscles. The question as to the exact requirements of the inorganic salts in the system has not yet been solved. According to Boussingault an adult requires from 60 to 90 mgrs. of iron daily, and according to König, persons upon a mixed diet require from 12 to 20 grams of sodium chloride. In reference to accessory foods, such as spices and condiments, extractives of meat, bitter principles contained in vegetables, tonics, and the alkaloidal beverages like coffee, tea and cocoa, we cannot stop to point out their physiological effects, except to say that, since they act largely through the nervous system, every excess over and above the amount required will produce mischief; indeed we may safely conclude that, while the use of accessory foods in moderation increases temporarily the elasticity of mind and body and a desire and capacity for work, their abuse is fraught with danger. FOOD. The two broad divisions of food are animal and vegetable, although the mineral kingdom unites to furnish man with sustenance. Animal food is characterized by a predominance of the proteids and mineral salts, while vegetable food is rich in carbohydrates, which, however, like the vegetable albumin, are enclosed in cells composed of a fibrous frame-work known as cellulose, and therefore more difficult to be acted upon by the digestive fluids. An excess of this cellulose usually excites undue peristaltic action and consequently a more rapid transit of the intestinal contents, and thus interferes with the complete utilization of the nutritive material; a certain amount of cellulose is necessary, however, to promote the action, because if the food was so nutritious as to be entirely absorbed, there would be very little solid to transmit and the action of the bowels would become irregular and unsatisfactory. Hence the good effect of graham bread, vegetables and fruit in habitual constipation. ANIMAL FOOD. MEAT. In a dietetic point of view we mean by meat the muscular substance with its connective tissues, the fat and various juices deposited therein. The nutritive value of meat depends upon the large percentage of protein. Dark meats, such as game and wild fowl and beef, contain from 18 to 25% of albumin. The relative amount of nutritive matter is shown in the following table based upon analyses by König, Voit and others: According to the foregoing table, game and fowl are richest in proteids, salts and extractives; veal and pork are poorest in proteids; veal richest in gelatin; ham and pork richest in fat; horse and veal poorest in fat; beef richest in extractives; veal poorest in extractives. All of which explains the superior nutritive value of game and wild fowl, in the so-called dark meats and also the superior flavor of beef and fowl over veal and pork, and also explains the rich amount of gelatin in veal-broth and gravies. The particular part from which the meat is derived also influences the percentage of proteids, as shown by König: |