Everybody knows what a disagreeable feeling is produced by keeping on such underwear after it has become dampened by perspiration, and this is due to the prevention of the dissemination of the exhalations from the body. Such disadvantages to the wearer of woolen underclothing may possibly be discounted by making such underwear with large meshes; but even in this case it is not easy to prevent the loss of porosity after washing. It is therefore advisable to wear a large meshed linen garment next the skin under the woolen underclothing; there will thus be a cushion of air between the skin and the woolen garment; and linen also has a great affinity for absorbing moisture and rapidly giving it off again. All kinds of underwear, whether of wool or other material, should be loose about the body. It is a great mistake to have it too tight. There should always be a considerable layer of air between the clothing and the skin. This layer is warmed by the blood at the surface of the body, and as air is a bad conductor of heat, even in the case of underwear not so thick as wool, if such clothing is worn somewhat loosely about the body and is porous, we shall not feel cold. The porosity of the tissue permits the entrance of air, and such tissues, with air in their pores, are abstracting a minimum of heat from the body, though such pores in the tissue allow for the free passage and exit of the harmful exhalations and evaporations from the body. From the foregoing it follows that socks which do not fit too tightly but fairly loosely, and which are made of porous material, such as good wool, will also be the warmest. It is quite unnecessary to adopt heavy double socks which fill up all the space in the shoes; as a matter of fact in such a case we may have colder feet than if we wore light porous good woolen socks that do not fit too tightly. Linen possesses the great advantage that it easily absorbs moisture and easily gives it off again, but as it is not such a bad conductor of heat as wool, and freely gives off heat, it may most advantageously be utilized in warm weather, and also in winter if worn under the other woolen garments. Linen is superior to wool in so far as the matter of cleaning it is concerned, as it can be washed much more thoroughly than wool, which easily retains dust and dirt. Linen is one of the most porous substances for underwear.