Besides water and fat, the skin excretes carbonic acid, and the different decomposed products of fat—such as lactic, formic, and butyric acids—to which the sour odor of perspiration is due. Much carbonic acid is dissolved in the perspiration, and escapes with it. Thus, it is not difficult to see that the kind of covering which acts as the best conductor of moisture and its impurities, and at the same time is a bad conductor of heat, and prevents its escape, is that which we must adopt as the healthiest and the cleanest. The power of absorption by vegetable life, of the poisonous emanations from animal life, is well known, and this process is not limited, it would appear, to living plants, but is continued by vegetable fibres—such as linen and cotton—with this difference, that the living plant assimilates these emanations and the dead fibre does not, but exhales them again when wetted or warmed. Thus our clothes, in consequence of their vegetable character, attract and retain these noxious principles which should by rights be immediately thrown off. Animal materials, such as wool, are made by nature—according to Dr. Jaeger—to protect animal life, and will neither attract noxious emanations nor prevent their evaporation from the body. This is shown, he observes, by the sense of smell and by the unpleasantness noticed in cotton and linen underclothing, linings, and apparel which have been long worn. There are many people to whom these considerations have a vital and especial interest. Certain skins perspire much more freely than others. This peculiarity occurs in persons of rheumatic and consumptive tendencies, even when quite free from actual disease. Women in middle age, also, and all in whom the circulatory system is weakened from any cause, have this tendency. But the people to whom, in addition, the Jaeger system appeals the most are certainly those who are corpulent, or show any tendency to become so. And as this point will probably interest many readers, I will give a brief notice of what Dr. Jaeger says on the subject. To be in what we English people call “good condition” there must be a correct proportion of the most important bodily constituents—viz., albumen, fat, and water. The first is the foundation of nerve, muscle, blood, etc., and in fact sustains the existence of the body. Relatively to albumen, water and fat may be viewed as auxiliaries, although they are indispensable in themselves. A proper condition of body requires that these three constituents shall be present in certain proportions, while the richer the body is in albumen the sounder it will be, and the fitter for work. On the other hand, any excess of fat or water will lessen its energies, and its power of repelling the action of influences likely to promote disease.