The essential thing in massage is the kneading of the muscles. We thus artificially increase the flow of the blood in them through the local irritation of the skin and the mechanical diffusion of the blood in the direction of the muscle. We thus produce artificial hyperæmia, not unlike the effects of a mustard plaster, and, in the same way as the plaster, we are also drawing blood from the congested organs, and especially from the engorged heart; thus we obtain a better distribution of the blood throughout the body and facilitate the action of the heart. It has been shown by the experiments of Sir Lauder Brunton and Tunnicliffe that kneading the muscles increases circulation through them in the same manner as massage. They found that during such kneading the amount of venous blood which issued from them was sometimes diminished and sometimes increased; that just after the kneading was over the flow diminished (apparently from the blood accumulating in the muscles), and this diminution was again succeeded by a greatly increased flow. The clinical results are precisely what one would expect from increased circulation in the muscles, and cases apparently hopeless sometimes recover most wonderfully under this treatment. By means of massage the functions of the heart can thus be facilitated, for massage mechanically diminishes the resistance of small capillaries to the oncoming blood-waves sent from the heart. It mechanically quickens the circulation of the blood through the capillaries by dilating them in a way similar to exercise (see, also, Chapter XVIII). By certain massage movements applied to the exterior region of the heart—such as vibratory massage—this organ can also be favorably influenced; and by kneading, friction, and massage together applied to the periphery of the body, and by passive movements of the extremities, many cases of heart disease have been treated with good results, and premature death prevented. Still more thorough is the effect of such treatment if carbonic acid baths are used in connection with the above, as at Nauheim, for such baths stimulate the skin, which becomes better provided with blood. We have referred to the effect of such baths in a previous chapter on the hygiene of the skin and kidneys by means of bathing. The Nauheim treatment affords good results in mild cases of arteriosclerosis, dilatation of the heart, and various other forms of heart disease. Massage is also an excellent thing in chronic diseases of metabolism, as it helps the resorption of waste products and augments the processes of oxidation; in cases of gout, obesity, and also diabetes, it can therefore give very good results.