The modes of classification glimpsed at are certainly exceedingly broad and sweeping. It is well enough to establish types and classes. But beneath them are sheltered the infinite possibilities of permutations and combinations, which explain the countless variety and complexity of form and function. Every individual born among the vertebrates, for example, must have a certain definite amount and percentage of pituitary gland, anterior and posterior, pineal, thyroid, parathyroid, thymus, adrenal, pancreas, interstitial and so on. Now if, to state it in terms of percentages, for the sake of argument, the pituitary is 25, the pineal 10, the thyroid 36, the parathyroids 15, the thymus 29, the adrenals 60, the pancreas 49, the interstitials 72 (the gland when acting maximally to be graded as 100), we see at once how different such an individual must be from one who has, say, pituitary 84, pineal 39, thyroid 26, parathyroid 42, adrenals 96, pancreas 22 and interstitials 89. One obtains at once from the contrasts of such figures some idea of the possibilities. As each point plus or minus must count to produce some difference in the individual, the results are manifest. Varying within the numerical limits imposed by genus, species, variety and family (which limits are probably responsible for the persistence of the particular genus, species, variety, or family) the individual becomes an individual because of the relative values of the percentages in his blood and tissues of these different internal secretions. We thus begin to gain an insight into the patterns according to which men, women and animals are woven.

We are, as yet, far from an exact endocrine analysis of the individual. But we know that the endocrines rule over growth and nutrition, a vast dominion which incorporates every organ and every tissue. By enhancing or retarding the nutritional changes, the growth of the organ or tissue is favored or restricted. The size and shape of an individual, as a whole, as well as of the specialized cell masses composing him, as hands and feet, the nose and ears, and so on, are therefore controlled by them. Whether an organism is to be tall or short, lean or corpulent, graceful or awkward, is decided by their interactions. These, like human covenants, vary with the different reactions of the parties to the contract. And so a great deal depends upon whether they work harmoniously or discordantly, and upon which does the most work and which the least.

Undersecretion and Oversecretion

It is when a gland, either in the course of development, or because of the influence of starvation, shock, injury, poisoning or infection, begins to undersecrete or oversecrete that its effects upon growth and nutrition become grossly manifest. A veritable transfiguration of the individual may occur, the black magic of which may perplex him for a lifetime. A man, made eunuchoid by an accident or by mumps, will observe in himself astonishing changes in his constitutional make-up, mentality and sexuality. He would be more astounded to learn that beneath the appearances, the changes, so alarming him, there are profound alterations in the rate at which he is taking in oxygen, burning up sugar, accumulating carbon dioxide and excreting waste byproducts through the kidneys, which are responsible for them.

The differences between the normal and abnormal are only a matter of degree. And so, to be sure, are differences between types. But it is hard to realize that the striking distinctions between the thyroid type and the pituitary, comparable, as said, to the differences between a greyhound and a bull-dog, are dependent solely upon quantitative variations in the general and local speeds of metabolism, among the cells.

DIVISION OF LABOR

Besides the antagonisms and co-operations between them, there are certain lines along which the glands, in their effects, specialize. The thyroid, for instance, is concerned specially with the regulation of the shape, form and finish of an organ. The pituitary shines at the periods of developmental crises, determining them and modifying them. It exerts the greatest influence upon the time of eruption of the teeth, both the temporary and the permanent, the onset of puberty, the recurrence of menstruation in women, and the time of occurrence of labor. The interstitial glands distribute the basis of the powers and limitations of masculinity and femininity. Abnormalities of these glands also affect the individual all along the line, in all of his aspects. So affected he may apparently change into a wholly different being. He may change in size, in the shape of his head, feet and hands, as well as in his habits, aptitudes and dispositions. So he may find it necessary to purchase an entirely different size of hat, more commodious clothes, and newly fitting gloves and shoes. At the same time, his family, relatives and friends, discover that the erstwhile generous, frank, neat and punctual and liked, has become stingy and suspicious and slovenly and hated. And all because a gland has begun to undersecrete or to oversecrete. The transformation will be slight or marked, depending entirely upon the extent of impairment, positive or negative, of the gland involved.

But it is not only in the shaping of the normal individual's architecture that the internal secretions dominate. Over that subtle something known in all languages as vitality, expressive of the intensity of feeling, thought and reactions in cells, they rule supreme. Gay vivacity and grim determination, the temperament of a Louis XIV, and the soul of a Cromwell, are the crystallizations of these chemical substances acting upon the brain.

INTERNAL SECRETION VARIETIES

There is no better way of illustrating the influence of the internal secretions upon the normal than the analysis of the variation of traits with variations in glandular predominances. The general build of an individual, his skeletal type, the proportion between the size of his arms and that of his legs, as well as that between his trunk and his lower extremities, whether he is to be tall, lanky and loutish, or short, squat and dumpy, are to be considered. Different facial types are the expressions of underlying endocrine differences. The head and skull offer a number of clues to the controlling secretions in the blood and tissues. Whether the forehead is to be broad or narrow, the distance between the eyes, the character of the eyebrows, the shape and size and appearance of the eyes themselves, the mould of the nose and jaws and the peculiarities of the teeth, are all so determined. The skin, in its color, texture, the quantity and distribution of its fatty and other constituents, eruptions and weather reactions, is influenced. Also the mucous membranes, the color and lustre and structure of the hair, as well as its general distribution and development, are hieroglyphics of the endocrine processes below the surface. Whether the muscles are massive or sparse, atrophied or hypertrophied, soft or hard, easily fatigable or not, bespeak conditions in the glandular chain. In short, we must regard the individual as an immensely complicated pattern of designs traced by the hormones as the primary etchers of his development. Though it must be admitted that the number of unknown and unsolved relations in the pattern are still enormously great, enough has been established to make possible a rough working analysis of the particular, unique organism placed before us for examination as Mr. Smith, Mrs. Jones, or Miss Smith-Jones.