COLDS.—As a means of protection against too marked a reduction of the temperature of the body—which normally is 98'6°F.—man is covered with skin. The adipose, or fatty tissue, which is found beneath the skin also contributes in this function. Fat, being a poor conductor, retains the body-heat and prevents too marked a reaction to the temperature of the environment, which, were it otherwise, might be injurious to the body. In temperate and frigid climates this layer of fat is not sufficient ; and hence clothes are necessary. These are likewise poor conductors of heat, and represent, as it were, an external layer of adipose tissue. The skin is supplied with numerous blood-vessels, which are kept in a certain state of contrac tion or of expansion by the nerves. If the skin is acted upon by variations in temperature, which are felt as cold or as heat, the nerves in the skin convey an impulse to the cord, from where impulses which cause either a narrowing or a dilatation are sent to the blood-vessels.
The stimulus of cold narrows the blood-vessels, causing less blood to flow through the skin. In this manner less blood is exposed to refrigera tion, and thus too marked a cooling of the body is prevented. But if the blood-vessels do not contract rapidly on the stimulus of cold—that is, if they have lost their capacity of reaction ; as, for instance, in consequence of weakness—this self-protective mechanism of the body is impaired, and a large quantity of blood is cooled. The greatly refrigerated blood acts upon
the internal organs and disturbs their activity, so that the many substances which should be excreted by these organs are retained in the body. As a result discomfort and chilliness, the first signs of a cold, manifest them selves. If there happens to be any organ which has been weakened by a previous disturbance, that organ will be the first to suffer from the conse quences of the cold, and will become the seat of a fresh attack of congestion. This renewed weakening of the affected organ permits the colonisation of bacteria, which multiply, and thus may give rise to the various disorders resulting from exposure to cold.
In order to prevent a cold, it is important to maintain a healthy, well nourished skin, which is rich in blood and capable of reacting to cold stimuli (see HARDENING), and also to keep up a moderate layer of fat on the body. In the early treatment of a " cold " it is important to induce profuse action of the blood-vessels of the skin, up to the point of sweat-formation ; this may he clone by means of packs, hot baths, hot beverages, elder-tea. etc. The patient should also take an enforced rest, preferably in bed, in order to permit the readjustment of the circulation in the various organs of the body.