Local hot water, sand, and mud baths are used to promote absorption only after or during chronic torpid processes, and are excellent treatment much less generally used than they deserve. The water baths can easily be arranged in any house, as is also the case with the more uncommon sand baths. Mud baths, which are really better, can rarely be used except at watering places. The effect of these baths is due to their thermic properties, and the benefits derived from them depend entirely on how they are given. I usually recommend my patients to take them as hot as they can comfortably bear (about 42° C), to immerse not only the affected joint, but a good part of the extremity above it, and to use enough water, sand or mud, as the case may be, to keep the temperature from falling too much during the bath, which ought to last about half an hour. I have never used any additions to mud baths. If one wishes to add anything to a water bath, ordinary sea-salt or cooking salt is just as good as the varieties of lye or the "spring salts," which are generally expensive, and the use of which is of advantage chiefly to the manufacturers ! (The massage seance should immediately follow the bath, which is taken once a day.)

The kind of baths just described have recently been partially replaced by baths in rarefied air, hot air baths, light baths, especially electric light baths. All these have very much the same effects as the others, but have an advantage in being more attractive and of more even temperature. Higher temperature is of no importance; a local bath in dry air at 100° C. to 114° C. does not heat the tissues more than a local mud bath at 42° C.; should the tissues be raised to a higher temperature than this (42° C.) certain proteids would coagulate and severe disturbances would result. It is not really known whether the electric light baths, beyond the effect due to their heat, have any effect deeper than the skin due to their wealth of ultra-violet "chemical" rays. Local baths in rarefied air were introduced by Junod in 1834, were in fashion for a short time, and have lately been taken up again by Bier. He encases the affected limb in appliances of various shapes, generally consisting of a firm glass case, open at one end or at both ends, which is connected with an air pump. This treatment is applied twice a day for ten to thirty minutes. India-rubber cuffs and bandages are used to keep the case air-tight, and it depends on the way in which these are applied whether the consequent hyperemia is passive or active. If the bandages are applied comparatively loosely and the air rarefied comparatively little, an arterial hyperemia results. If the bandages are applied tightly and much air is pumped out, a passive hyperemia results, both because the bandages press heavily and because the atmospheric pressure forces the indiarubber cuffs firmly on to the skin.

For hot air baths, which produce arterial hyperaemia, Tallerman's and Bier's appliances are the most suitable. Various modifications of the latter kind are to be had at the present time. They consist of boxes of various substances in which the air can be heated by means of gas or spirit or (in Lindemann's apparatus) by electricity. These enclose the affected joint and at the same time are air-tight. They are used like the former in the treatment of practically every kind of chronic disease of joints, traumatic, rheumatic, or bacterial, and powerfully promote absorption (through the hyperemia which they cause) relieve pain, and restore mobility. Treatment is given for an hour daily. The temperature of the air in such an apparatus may be 100° C, or at the highest 114° C*

To Kellog we owe the construction of an electric light bath for local treatment.

Electromotor air douches are also used (Frey, Taylor, and others). Hot air is used in neuralgic and spastic conditions. But there are arrangements with two systems of pipes, one for very hot and one for cold air (to about - 10° C). Such arrangements, which provide hot and cold currents of air alternately, are used to hasten absorption after joint affections with exudation.

The Scotch douche of hot and cold water alternately is even more valuable than the above in its effects, for a strong movable pressure, which can be called water massage, is here combined with the thermic effects.

But the most important hypera?mic treatment is most decidedly that recently recommended by Professor Bier of treating by means of slight, but only slight, stasis, produced by an elastic bandage applied centrally to the diseased part.