This is a fat soluble vitamin and is found chiefly in the green leaves of plants, tomatoes, butter, sweet potatoes, yellow corn, green peas, cream, egg yolk, palm oil, broccoli, kale, dandelion, parsley, lettuce (there is thirty times as much vitamin A in the outer as in the inner leaves of lettuce), spinach, apricots, yellow peaches, etc.

All yellow vegetables and fruits are sources of this vitamin, or rather carotene, which is pro-vitamin A. Provitamin A is converted into active vitamin in the liver. Carotene is also found in green plants where it is masked by the chlorophyll. "The solids of tomatoes," says Carque, "contain more of vitamin A than butter fat." The cream and butter of the Jersey cow is especially rich in carotene when there is an abundance of green pasturage. This is not so of the butter and cream of the Holstein. It is claimed that the Holstein converts the carotene into vitamin A with greater efficiency than does the Jersey. This may and may not be true.

White varieties of corn, potatoes, asparagus, celery, lettuce and turnips are deficient or devoid of vitamin A. Bleached vegetables are lacking in this substance. Vitamin A may be stored in the liver, in fat and in milk.

Lack of A checks growth, hence it was formerly called the growth-promoting vitamin (in keeping with the rest of their nomenclature, it should have been called the anti-dwarf ing vitamin) but since it is now realized that there are several dietary deficiencies that stunt growth, vitamin A has been renamed the antikeratinizing vitamin.

Keratinization is the acquisition of a horn-like character by the epithelial tissue in many parts of the body. This is to say, the epithelial tissue becomes like the outermost layer of the skin. It then loses function. The epithelium atrophies. Such conditions as dry skin, night blindness, zerophthalmia, defective enamel formation in the teeth, changes in the tissues and glands of the mouth, digestive tract, respiratory organs, urinary and genital tract, and keratinization of other structures are attributed to vitamin A avitaminosis.

Vitamin A deficiency is credited with the following abnormal developments:

1. Failure of the processes of growth.

2. A greatly reduced resistance to infectious agencies.

3. Failure in the development of bone, cartilage, and teeth and in calcium metabolism.

4. Tendency to edema.

5. Failure of the nutrition of the cornea.

Deficiency of vitamin A is supposed to be concerned in the development of rickets, keratomalacia, deficient calcification of the teeth, nutritional edema and phosphatic urinary calculi (stones).

Vitamin A is destroyed by oxidation, so that when foods are chopped or ground this vitamin is lost. Grated carrots have far less vitamin A than whole carrots. Long cooking in an open kettle also results in loss. It is not affected by heat, but is injured by being exposed to light and especially by being exposed to ultraviolet rays. Freezing does not affect it.

The estimated average daily requirement of this vitamin is 5,000 units. More is required by infants and children and by pregnant and nursing mothers. Children and mothers need an abundance of fruits and vegetables.