To take a single instance, the development of the long bones is dependent upon the handling of food lime by the body. Eunuchs and eunuchoids, that is, individuals with insufficient internal secretion of the interstitial cells, have longer bones and more fragile bones than the normal. Vice versa, those with an excess of the secretion have shorter and thicker bones. The earlier the onset of menstruation, which means puberty, the shorter the extremities, as the action of the internal secretion of the ovaries closes the story of the growth of the long bones.
The ovaries are a most important factor in the regulation of the power of the organism to keep lime in the bones. If they over-secrete in an excess which cannot be taken care of by the other glands of internal secretion, the body loses lime, a softening and curving of the bones occurs, and the most horrible deformities and tortures for the sufferer. Taking out the ovaries has cured some of the afflicted. Administration of the antagonizing gland extracts has helped others. An Italian, Bossi, in 1907, used adrenal gland curatively. More recently, a British student of the subject, Blair Bell, was given the direction of the treatment, at long range, of a number of cases in India, the land of chronic pregnancy with insufficient food, and consequent oversecretion of the ovaries, with the typical softening of the bones. At his suggestion pituitary was used successfully.
Some of the glands of internal secretion act as accelerators to the sex glands. Others act as retarding antagonists. Among the most important of the latter is
THE THYMUS
The thymus is the gland which dominates childhood. It appears to do so by inhibiting the activity of the testes or ovaries. Castration causes a persistent growth and retarded atrophy of the thymus. Removal of the thymus hastens the development of the gonads.
Situated in the chest, astride the windpipe, it descends and covers over the upper portion of the heart, overlapping the great vessels at the base of the heart. It is a brownish red mass, which when cut presents the spongy effect of a sweetbread. The more intimate view of detail revealed by the higher powers of the microscope shows conglomerations of the white cells of the blood known as lymphocytes. But scattered through the substance of the gland, between these lymphocytes, like the interstitial cells of the sex glands placed between the sex cells, are peculiarly staining cells in whorls. Of which there are many more in the thymus of embryonic and early postnatal life, known after their discoverer as Hassal's Corpuscles. They are believed by some to elaborate the specific internal secretion of the thymus. Present in all vertebrates, there seems to be more of it in the carnivora than in the herbivora, like the thyroid.
Concerning the exact function of the thymus, we are a good deal at sea. The latest opinion about the results of extirpation even in young and growing animals is that they are nil. Yet there is a certain justification for proclaiming the thymus the gland of childhood, the gland which keeps children childish and sometimes makes children out of grown-ups. There is a quantity of data for that proposition. In the first place, the curve of rise of growth of the gland seems to coincide with the period of childhood, the curve of its decline with the period of adolescence and the rise of the sex glands. In the past, it was accepted, that with puberty the thymus atrophied and was replaced by some sort of fatty tissue. Nowadays, it is held that secretion cells persist throughout life. When the extent of this persistence is too great, the gland being from five to ten times as large as the normal, a number of other features become prominent to make the extraordinary individual, the status lymphaticus, who amid the hazards of life will react in an extraordinary way. He will be taken up in the consideration of internal secretion personalities.
Then there are the varied and remarkable phenomena of thymus enlargement and hyperactivity in childhood itself. When an enlarged thymus is present in an infant, the initiation of breathing in the new-born, the introduction of the newcomer to the oxygen of the air, may be an exceedingly prolonged, difficult, matter. Such a baby is said to be born blue, and the breathing may be stridorous for days, becoming normal for a time, to be followed later by spells of trouble in breathing, breathlessness or breathlessness with blueness, and threatened extinction. Sometimes these spells come out of a clear sky in an apparently healthy child. That some poison, probably an oversecretion of the thymus, is responsible is shown by the relief obtainable by X-ray shrinkage of the gland, or the surgical removal of a part of it.
Moreover, the gland is influenced by and influences the factors of body weight and growth with an extreme readiness and lability. Deficient general undernutrition leads to rapid decline in its weight. Back in 1858, the pioneer student of the thymus, Friedleben, declared that the size and condition of the thymus is an index to be the state of nutrition of the body. Underfeeding for four weeks will reduce it to one thirtieth the normal. It seems to act as a storage and reserve organ, affording some protection against the limitation of growth by lack of food material. In exhausting or wasting disease, the weight of the gland sinks much more quickly than other glands. Scattered instances have been reported of children growing, putting on inches in height and expanding mentally, when thymus was fed to them, in whom every other measure previously tried had failed. A French study of over four hundred idiotic children with normal thyroids reported that over three fourths had no thymus at all. Everything points to the most direct and close relation between the gland and nutrition and growth, but with nothing tangibly definite like our knowledge of the thyroid and the pituitary.
There is evidence that the thymus is involved in the health and efficiency of muscle cells and muscularity. Certain tumors of the thymus, presumably destructive of the gland substance proper, and thus cutting off its secretion, are accompanied by a singular muscle weakness and atrophy of the muscle cells, entirely out of proportion to the general damage suffered by the other cells of the body when affected by the poison of a malignant growth. Also, the thymus has been discovered diseased in certain mysterious progressive muscular wastings. A remarkable fatigability of muscles, which appears after the slightest exertion, is a feature. The feeding of thymus has caused muscle cramps which apparently depends upon an increased excitability of the muscle nerve endings.