Opposed to the alteratives are an important class of drugs which diminish metabolism. Alcohol has this action, apparently by being itself so readily oxydised in the tissues that it robs the cells, as it were, of oxygen, while it also binds the oxygen more firmly to the red corpuscles, and thus in two different ways spares tissue change. Quinia also lowers oxygenation, and has a further influence in preventing oxydation of protoplasm, which is imperfectly understood. Probably Alcohol, Quinia, Resorcin, Kairin, Chinolin, and Salicin, also diminish the activity of the natural metabolic ferments.

Complex Measures.-Some of the most powerful means at our disposal for influencing nutrition are a combination of the preceding measures. The best illustration of this is the treatment carried on at a foreign bath, we shall say at Aix-les-Bains, in Savoy. Here an English patient enters a new, a purer, and a warmer atmosphere. His food is reduced in quantity and changed in quality; he has to take active muscular exercise; he enjoys a daily bath, which is really a complex arrangement of washing, rubbing, douching, and frequent change of surface temperature: and he has to drink a definite amount of the waters, which contain Soda, Lime, Magnesia, Iron, and Iodine. Such a combination of measures is manifestly powerfully alterative.

Tonics, which increase the tone or general muscular and nutritive vigour, belong, as we have seen, to several of the preceding classes.

III. Pathological Relations

The disorders of metabolism are many and complex. Diseases so wide apart as gout, syphilis, and malaria, and disorders so different in their cause and effects as fever and fatty degeneration, are linked together by the fact that they are all affections of nutrition. In this place we can refer but to a few of them, and that very briefly.

The cause of metabolic disorder is most frequently found in the ingesta. An excessive supply of lymph to the active cells, an unnatural richness of the blood in proteids from indulgence in food, or an insufficient supply of oxygen from insufficient exercise, will disturb general metabolism as they disturb hepatic metabolism, and contribute to the production of the diseases known as obesity and gout. Deficiency of plasma is a result of anaemia, as we saw in the last chapter; and since it generally accompanies aglobulism and deficiency of oxygen, the result is feebleness of metabolism throughout the entire body. Metabolism is also disturbed by sudden and extreme alterations of external natural influences, such as the temperature, moisture, pressure and electrical condition of the air; and local changes of temperature give rise to chills, colds, and rheumatism. The opinion, however, is daily growing that fever and many other disorders of metabolism are often due to the entrance into the tissues of unnatural, extraneous, or infective substances, whether inorganic, organic, or organised, such as foul air, the contagia of measles, scarlatina, and other exanthemata, and the organisms of malaria, syphilis, and tuberculosis. It is suggested that these organisms interfere with metabolism by settling in the tissues and carrying on an indepent metabolism of their own, that is, by living, thriving, and reproducing their like at the expense of the pabulum of the tissues; that they throw the products of their changes into the venous current, which is thus poisoned and infects the rest of the body; and that by their life-changes they cause a development of heat which constitutes one part of fever.

The 'phenomena of disordered metabolism are necessarily of endless variety and complexity. The most striking symptoms attend that kind of excessive nutrition known as fever, viz., wasting, increased excretion, high temperature, and general functional derangement. To this subject we shall return in chapter xiv (The Body Heat, And Its Regulation : The Skin). Inflammation may be broadly defined as a similar increase of metabolism in a local form. Defective local nutrition is seen in fatty and calcareous degenerations. In some forms of derangement the results are chiefly appreciable in connection with the tissues themselves, as in obesity; in others they are discovered in the excretions, e.g. gravel, and glycosuria; in many instances, such as gout, they can be found both in the tissues and excretions. Occasionally they take the form of excessive and unnatural growth, invading and destroying the normal structures, as in cancer. In other diseases the growth is rapidly followed by decay, as we see in syphilis and tubercle. When the derangement remains persistently, and establishes itself in the organs, without definite anatomical change, it constitutes in part the so-called diatheses-gouty, rheumatic, calculoid, etc. Manifestly in this great collection of diseased conditions we have an urgent demand for treatment.

IV. Natural Recovery

Experience has taught us that many of the most common derangements of metabolism, such as fever, gravel, and rheumatism, are of but temporary duration, that is, disappear spontaneously, when the normal conditions have returned or are restored. The forms which natural recovery takes in metabolic disorder are known as reaction and repair, i.e. increased nutritive activity, often associated with inflammation. Unfortunately this class of derangements are peculiarly liable to recur, but this is chiefly because of the return of unhealthy circumstances. Here, too, as elsewhere, recovery is limited by anatomical changes; but even growth and degeneration will sometimes disappear, under favourable conditions.

V. Therapeutics

The rational treatment of disorders of nutrition is a subject of such large proportions that it can be discussed only in an illustrative way in the present work. A careful consideration, however, of the principles laid down under the preceding heads will, it is hoped, enable the student to extend his knowledge practically on his account.

The general treatment of disorders of metabolism involves the regulation of the whole manner of living: of the food and air, the work done, the excretions, and, above all, the careful balance of these. Muscular and nervous exercise must be ordered in fair proportion, to prevent obesity and gout on the one hand, or exhaustion and degeneration on the other.