The extraordinarily well protected position of the pituitary, its persistence throughout life, and its abundant blood supply, emphasize its vital importance. No other gland of internal secretion can adequately substitute for it. Complete expiration means death, in two or three days, with a peculiar lethargy, unsteadiness of gait and loss of appetite, emaciation, and a fall of temperature, so that the animal becomes cold-blooded, its temperature the same as that of the atmosphere it occupies. If only part of the anterior lobe is taken away, there occurs a remarkable degeneration of the individual. The degeneration is not a mucinous infiltration of the skin and the internal organs which occurs with thyroid deprivation, but a fatty degeneration, with a tendency to inversion of sex. A singular somnolence, a dry skin, loss of hair, a dull mentality, sometimes epilepsy, and a noticeable craving for and tolerance of sweets appear. These are but a few of the observations obtained in experimental sub-pituitarism, that is, underaction or insufficient secretion of the pituitary, produced by removing part of the anterior gland. If such an experimental sub-pituitarism is started in infancy, for instance in puppies, there is a cessation, or marked hindering and slowing of growth. That is, dwarfs are artificially created. Apropos, pathologists have shown that in several true human dwarfs the gland is rudimentary or inadequate. All of which goes hand in hand with the evidence that the skeleton stands directly under the domination of the pituitary. REGULATOR OF ORGANIC RHYTHMS