=Proteins= are the tissue builders of the body. They are derived from meat, milk, eggs, peas and beans for example. Some foods are much richer in protein than others, and there is also a difference in the quality of the protein. Some protein is more valuable from the standpoint of food than others. Casein is very rich in protein which is of great food value. The protein found in meat is also of good quality, but it is not as valuable as that found in milk. Such cellular organs as the liver and pancreas furnish a good source of protein. There is a very small amount of protein of excellent quality found in leafy plants. There is a difference of opinion among authors as to the amount of protein needed per day by healthy individuals. Some advise a very small amount of protein while others recommend a diet containing as much as 125 grams, approximately four and one-half ounces, per day. The =carbohydrates= furnish the body with the necessary material for forming adipose tissue and heat through oxidation. It is very essential that the body be provided with sufficient starches. This is evidenced by the fact that starch constituents are so universally found in food from whatever source taken. For example, carbohydrates or starchy foods are found in cereals, tubers, such as potatoes, and sugars of cane, beets and fruits, and glycogen in flesh. =Fats= come from animal and vegetable sources and are represented by butter, fats of meat, olive oil, cottonseed oil, nuts and seeds. Oily substances are found in practically all vegetables. A vitamin known as fat soluble A is found in certain fats, but not in others. It is found in the fat of milk and usually in other fats of animal origin; and also in eggs and in leafy plants. Lard and oil of plant origin furnish very little of this vitamin. It can readily be seen by this that all fats do not have the same food value. The =condiments= are the spices such as pepper, mustard, cloves, coffee, tea and alcoholic beverages. =Inorganic= salts are not ordinarily classed as a food. However, it is essential in the maintaining of life. It performs a very important function in the building of bone and assists also in digestion and metabolism. The vegetable acids, such as tartaric from grapes, lemon and citric, will be found in combination with the bases calcium, sodium and potassium, for example, especially when they are taken from fresh vegetables and fruits. When absorbed they form carbonates and are therefore indispensable in the process of metabolism, since they aid in maintaining the alkalinity of the body. If the food of the growing infant is deficient in calcium phosphate, or if there is an interference with transmission which hinders the activity of calcium phosphate in the body, the bones of the child will be poorly developed and will become abnormally soft. In this case they yield under the weight of the body and become deformed. A good illustration of this is seen in rickets.