From each portion of the gland (to stick to the accepted nomenclature of speaking of the two glands as one) an active substance has been isolated.  Robertson, an American chemist, separated from the anterior lobe a substance soluble in the fat solvents, like ether and gasoline, which he christened tethelin.  But P.E.  Smith has shown that the active material is soluble neither in boiling water nor in boiling alcohol, the typical fat solvent.  A number of facts favor the idea of the anterior lobe cells as stimulants of growth of bone and connecting and supporting tissues generally.  From the posterior lobe, pituitrin, believed its internal secretion, has been obtained in solution.

Pituitrin is a substance of many marvelous functions.  In general, it controls the tone of the tissues, of involuntary or smooth muscle fibres of the blood vessels and the contractile organs of the body like the intestines, the bladder and uterus.  When injected, it will slowly raise the blood pressure and keep it raised for some time, and will increase the flow of urine from the kidneys and of milk from the breasts.  It will also cause an intense continued contraction of the bladder and the uterus.  It is also said to control the salt content of the blood upon which its electrical conductivity and other properties depend.  Normally, there is a certain fixed ratio of the salts in the blood, which keeps them like the ratio in sea-water.  Again, we have an example of the curious atavism of the internal secretions.  The thyroid, remember, keeps the iodine concentration of the blood like that of the ocean, our original habitat.  Pituitrin likewise does its part to maintain our internal environment as near as possible to what was once the surrounding medium.  A substance somewhat similar has been found in the skin glands of toads.

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.