Electrical atmospheric states and vicissitudes have, quite probably, a practical consequence beyond what is usually ascribed to them in connection with health and disease. But their effects are so difficult to disentangle from those of other meteorological causes that we must be content at present without attempting their exact specification. The same observation may be made with reference to ozone. Elevation of site has importance, not only in regard to climatic hygiene, but also to its therapeutic use, particularly in the treatment of phthisis, goitre, and some affections of the nervous system. But in our brief and general survey of Etiology this topic must be left without discussion, since no disorder appears to be traceable to elevation alone, beyond the temporary prostration on exertion, with hemorrhages from the nose, lungs, etc., often produced in those who climb to great mountain-heights or ascend rapidly in balloons. It has been shown by ample experience that considerable populations may live in ordinary health through long periods at altitudes more than 10,000 feet above the level of the ocean. Depression below the surface of the earth has never become a part of human experience beyond the limit of a few hundred feet. Miners living underground in a few places in Europe have been found to exhibit comparatively feeble health, but the privation of sunlight, the confined atmosphere, and the dampness of such unnatural abodes will suffice to account for these effects. Under functional causation of disease we may include all excessive, deficient, or abnormal exercise of any of the organs of the body. To simple excess may be ascribed the scrivener's or bank-officer's paralysis of the muscles of the hand used in continuous writing; brain {135} exhaustion from mental labor or anxiety, unrelieved by sufficient sleep; and sexual impotence, temporary or lasting (or sometimes even general paralysis), from inordinate sexual or sensual indulgence. Deficiency of functional exercise is observed to produce disability, as when the muscles of a limb, for instance, are for a long time restrained from use. Surgeons meet with this inconvenience (unless assiduously guarded against) when a fractured limb is kept long at rest in a fixed position. Atrophy of the mammæ in single women of retired lives is common; atrophy of the testicles in unmarried men much less so. These changes, however, are physiological, not pathological; upon alteration of conditions--_e.g._ marriage--the atrophy will disappear altogether.