and restore the normal condition. The patient notes the effect on the second day and often within a week is relatively quiescent. On the contrary, if there is thyroid deficiency there results the opposite state, a reptilian sluggishness. At will, then, through diminished, normal, or excessive administration of thyroid secretion, we may produce an adynamic, a normal, or an excessively dynamic state. By the thyroid influence, the brain thresholds are lowered and life becomes exquisite; without its influence the brain becomes a globe of relatively inert substance. Excessive doses of iodin alone cause most of the symptoms of Graves' disease. As we have stated, the active constituent of the thyroid is iodin in a special protein combination which is stored in the colloidal spaces. Hence one would not expect to find changes in the cells of the thyroid gland as a result of increased activity unless it be prolonged. We have thus far considered the normal roles played by the brain, the adrenals the liver, the muscles, and the thyroid in transforming latent into kinetic energy in the form of heat and motion as an adaptive response to environmental stimuli. The argument may be strengthened, however, by the discussion of the effect of the impairment of any of these links in the kinetic chain upon the conversion of latent into kinetic energy. Effect Upon the Output of Energy of Impaired or Lost Function of Each of the Several Links in the Kinetic Chain (1) _The Brain_.--In cerebral softening we may find all the organs of the body comparatively healthy excepting the brain. As the brain is physically impaired it cannot normally stimulate other organs to the conversion of latent energy into heat or into motion, but, on the contrary, in these cases we find feeble muscular and intellectual power. I believe also that in patients with cerebral softening, infections such as pneumonia show a lower temperature range than in patients whose brains are normal. (2) _The Adrenals_.--In such destructive lesions of the adrenals as Addison's disease one of the cardinal symptoms is a subnormal temperature and impaired muscular power. Animals upon whom double adrenalectomy has been performed show a striking fall in temperature, muscular weakness,--after adrenalectomy the animal may not be able to stand even,--and progressive chromatolysis. (3) _The Liver_.--When the function of the liver is impaired by tumors, cirrhosis, or degeneration of the liver itself, then the entire energy of the body is correspondingly diminished. This diminution of energy is evidenced by muscular and mental weakness, by diminished response and by gradual loss of efficiency which finally reaches the state of asthenia.