_The Tonic Effect of Cold Upon the System._—The effect of cold upon the muscles, when given in the form of a cold bath, douche, or spray, is to augment muscular energy and tone to a very great extent; this increased muscular tonicity is the cause of the slight shivering. The cold douche, if short,—one or two seconds,—and given with a pressure of from 25 to 30 pounds, is a powerful restorative in fatigue resulting from severe muscular effort, but it must be immediately preceded by a short hot bath, and must be followed by vigorous rubbing and wrapping in a hot blanket. Short cold applications cause elevation of temperature and increased metabolism, while prolonged cold applications cause a fall of temperature and decrease of metabolism. The tonic effect of cold water is believed to be due to the stimulation of the sympathetic nerve-centers. The sympathetic nervous system controls the blood-vessels, heart, the functions of secretion and excretion; and, indeed, all the vital functions of the body. The sensation of well-being which accompanies the reaction following a general cold application is largely due to an increased activity of the cerebral circulation. Cold water is a physiologic tonic, and the cold bath, properly employed, increases the vital resistance to pathologic processes. All applications of water at a temperature low enough to provoke vital resistance are tonic; hence, tonic effects are produced by all temperatures below 90° F., but the most certain and pronounced results are obtained from the douche in every form, which adds mechanical impact to the thermic effects of cold. The most durable tonic effects are produced by the frequent use of very cold and very short baths. A tepid bath causes a lowering of the body temperature. =The Chief Varieties of Baths.=—These, in the order of frequency with which they are used, are: ablutions; tub; foot-tub; sitz; salt sponge; shower; Turkish; horizontal jet; needle; fan douche; Scotch douche; Roman and electric-light baths. =Ablutions or Sponge Baths.=—These baths are of universal use. The sponge is one of the dirtiest and most impossible articles of the toilet to clean and to keep clean. It is a collector of dirt and germs, and should be banished from every bath-room and from every house. It is not sufficient that each member of the family should have her own sponge; it is quite possible for the individual to become infected or reinfected from her own sponge. Incidentally, it does not afford sufficient friction, and thus does not favor reaction. In taking ablutions, the application of water may be made with the hand, though it is best made by means of a wash towel. The good effects of the simple ablution will be greatly enhanced by the use of the hat tub, and this especially where there is no bath-tub in the house.