The first unknown factor, or vitamine, essential for growth and health, often called the fat-soluble growth-promoting substance, is found, in amounts sufficient for human needs, dissolved in the fat of certain foods such as milk, butter, cream, eggs, meat (if enough of it is eaten), cod-liver oil, soybeans. The following foods contain this unknown substance, or vitamine, in amounts which will help; they are too bulky to be used as its main source by the human being, but as a class they are the main source of this important substance in the diet of most of the domestic animals: leaves and stems of plants, such as spinach, Swiss chard, dandelion greens, cabbage, onion, celery.

The second unknown factor, or vitamine, essential for health and growth is soluble in water and is found in amounts sufficient for human needs in milk, eggs, breakfast foods and breads made from the whole cereal grain, peas, beans, and lentils. In fact, this substance is found in practically all naturally occurring foods. It is often called the water-soluble growth-promoting substance.