Innumerable experiments have been made, both on human beings and on animals, to determine the exact functions of the thymus gland. Does it give off some substance directly into the blood-commonly called an internal secretion-which would affect the growth of the body? The thymus is removed occasionally, and thus far no recognizable condition has been found which would be exclusively related to removal of the thymus. Neither has there been found any effect from taking large amounts of thymus extract, apart from the fact that it contains many important nutritive materials and is therefore helpful in the nutrition of the body.
When a child is born, the thymus is found as a closely packed mass of cells. This gland is large enough in many instances to occupy much of the space directly under the breastbone. Later in life the size of this glandular material decreases in relationship to the size of the body. Finally the gland disappears and is replaced by fat.
When there is a deficiency of material coming from the cortex of the adrenal gland the thymus is likely to enlarge, as well as the lymph glands elsewhere in the body. This has been called status thymicolymphaticus. Sometimes these patients die suddenly; death has been attributed to the enlargement of the thymus, whereas it was actually due to the deficiency of the secretion of the important material from the cortex of the adrenal gland.
Sometimes people who have a condition called myasthenia gravis, in which there is the development of serious weakness and incapacity, have been found to have enlargements of the thymus gland.
It has been thought that removal of this gland surgically or breakdown of the gland by exposing it to X-ray would be helpful in such cases. While some of the patients seem to improve, others do not. One is not quite certain whether the improvement was merely a coincidence and would have occurred anyway, or is in some way related to the treatment. Recently attempts have been made to treat this condition with ACTH. Some have said that great benefit has been brought about, but others indicate that cases have become worse. This would indicate that ACTH does have an effect in changing both the mental attitude of these patients and also perhaps the general constitution. The drug does not appear to be a specific drug for the treatment of myasthenia gravis.
Physicians now believe that the thymus, being composed of lymphoid tissue and containing a high concentration of essential substances, is a storehouse for aid of the body which is directly under control of other glands and a part of the interlocking gland system of the body.