FOR some considerable time, the true significance of several small, functionally obscure organs in the human body has been a vexing question. Finally it was found that they contain important chemical constituents which they pour into the blood-circulation. These substances are of great importance for the body-metabolism.
It has been observed that after radical extirpation of such an organ as the thyroid gland for exophthalmic goitre, the patient begins to suffer from general trophic disturbances, such as puffiness of the skin, dry epidermis, slowing of all mental activities, which might go on to complete imbecility.
These symptoms will at once abate if the patient is given small portions of the thyroid gland, e.g., that of the sheep, or thyroid extract. It was further noted that the same treatment proved effective in the case of patients suffering from the same symptoms, which had manifested themselves spontaneously, without any operation.
A small portion of this organochemical substance acts as a stimulant to the tissue metabolism. It cures obesity, renders the epidermis lustrous, and even improves cretinism, whereas a larger dose acts as a heart-poison, which may be observed by the acceleration of the pulse-rate. As far as the life is concerned, it may be added that, in a child in whom the thyroid gland is removed at an early period of its life, maturity is retarded or prevented altogether.
At first it was believed that organs which furnished such extremely active substances, represented a new type of gland. As no efferent duct was found, their activity was referred to as "internal secretion," a term which is self-contradictory. But more and more such organs with active products were subsequently discovered, e.g., the thymus, the supra-renal bodies, the hypophysis (pituitary), etc.