It is all as if a baby were suddenly to grow a beard and moustache, evolve and shed teeth, and acquire the manner of an earnest citizen, and yet retain the height and weight of a baby. That the spectacle of such a superbaby is not quite the most fantastic of all improbabilities is shown by the condition of progeria, first recorded by the Briton, Hastings Guilford. A queer spectacle in which a child incontinently grows old without having lived—in the course of a few weeks or months. You look upon him and see senility on a small scale, but with all its peculiarities: wrinkled skin, apathy, gray hair and all the rest of it. All we can say about it is that it is probably due to a paralysis of all the glands of internal secretion, a removal of their influence upon the cells. Contrariwise to the feeding of thyroid, removal of the thyroid of tadpoles will prevent their development into frogs. If iodine is then fed to them, say mixed with flour, normal metamorphosis will occur. If Body is the tool chest which we carry about with us, as Samuel Butler said, then to the thyroid belongs the name of tool-maker.
Another function of thyroid that must be taken into consideration is what has been spoken of as its antitoxic function—in plainer English, its power to prevent poisoning, or to increase resistance against poisons, including the bacteria and other living agents which cause the infectious diseases. Each molecule of food, ingested for assimilation into our substance, accumulates a history of wanderings and pilgrimages, attachments and transformations beside which the gross trampings of a Marco Polo become the rambling steps of a seven-league booted giant. In the course of its peregrinations, it becomes a potential poison, potential because it is never allowed to grow in concentration to the danger point. The thyroid plays its rôle of protector like all the internal secretory machines. In an animal deprived of a thyroid the feeding of meat shortens life—a single sample of how it works to guard against intoxication from within. The feeding of thyroid will also raise the ability of the cells to stand poisons introduced from without—intoxications of all sorts. Alcohol and morphine will affect in much smaller doses the subthyroid person than the normal or the hyperthyroid. As regards the infections, which directly or indirectly kill most of us, the injection of thyroid will increase the content in the blood of the protective antibodies which preserve us, temporarily at any rate, against malignant invaders. The opsonins, for example, those substances which butter the bacteria so that the appetite of the white cells for them is properly roused, are mobilized by thyroid feeding or injection. Other substances in the blood which destroy and dissolve bacteria are also increased. The thyroid probably performs these functions by sending its secretion to the cells directly responsible for the immunity reactions, and stimulating them to activity.
A sketch of the thyroid like the foregoing shows it as the wondrous controller of vitality and growth, and indefatigable protector against intoxicants and injuries. When it is sufficiently active, life is worth while; when it is defective, life is a difficult threatening blackness. That would make it out as the gland of glands. It is tremendously important, without a doubt, in normal everyday life. But no more so than the other members of the cast. The position of star it may claim, but in vain. The other glands of internal secretion to be sketched will each, when the marvels of its business in the cell-corporation are considered, present itself as candidate for the honors of the president. Justice should give fair credit to all the organs which fabricate the reagents of individuality, and the regulators of personality.
THE PITUITARY
In the human skull, the pituitary is a lump of tissue about the size of a pea lying at the base of the brain, a short distance behind the root of the nose. It is of a grayish-yellow color, unpretentious and insignificant enough in appearance, and so long neglected by the scientists who boast their immunity to the glamor of the spectacular. Guesses at its nature date back to Aristotle.
Like most of its colleagues among the glands of internal secretion, it is really two glands in one, two glands with but a single name. At least it consists of two different parts, distinct in their origin, history, function and secretions, but juxtaposed and fused into what is apparently a homogeneous entity. They are conveniently spoken of as the anterior gland and the posterior gland.
In the embryo, the anterior gland is derived by a proliferation of cells from the mouth area. The posterior gland represents an outgrowth of the oldest part of the nervous system. When it is traced back along the tree of the vertebrate species, it is found to be present in all of them. An ancient invention, its precursor has been identified in worms and molluscs and even among the starfish. "The pituitary is practically the same, from myxine to man." A trusted veteran, therefore, among the internal secretory organs, its importance can be surmised.
To understand the story of the pituitary, variously acquired bits of information concerning it have been assembled and fitted together like the fragments of a picture puzzle, as Cushing has so well put it. Here and there pieces stick out, obviously out of place. The relations of some of them to one another or to the whole design are not at all clear. Parts appear to have been irrevocably lost, or not yet to have turned up. Chance bystanders will select odd figures and articulate them into a new harmony. Yet out of the jumble of fragments, a fairly respectable insight has been gained in less than a half century.
The pituitary is cradled in a niche at the base of the skull which, because of its form, is known as the Sella Turcica or Turkish saddle. So situated, an operative approach to it is overwhelmingly difficult. On the other hand, X-ray studies are favored. "Nature's darling treasure" it might be called, since there has been provided a skull within the skull to shelter it.
Under the most highly magnifying lenses of the microscope, three kinds of cells have been distinguished. The anterior gland is a collection of solid columns of cells, surrounded by blood spaces into which their secretion is undoubtedly directly poured. A gelatinous material, presumed to be the internal secretion of the gland, has, in fact, been observed emerging from the cells into the blood spaces. The posterior lobe, or gland, consists of secreting cells producing a glassy substance which finds its way into the spinal fluid that bathes the nervous system. The spinal fluid itself is a secretion of another gland at the base of the brain, the choroid. Nerves and internal secretion are associated here with a closeness symbolic of their general relations.