natural philosophers tell us there is no such thing as cold; it simply implies in an arbitrary manner a low degree of heat. An atmosphere which feels cool to some persons is not so to others. In the next place, by taking cold, one intends to express that the body is affected by a definite set of symptoms, for which the phrase is not appropriate. We do not say, "I have taken heat," or "I have taken damp," although these influences produce disease as well as cold. Nevertheless, the expression in question is sanctioned by usage, and is well understood, since every one in his own person has experienced the symptoms which go to make up the condition of having a cold. The affection is termed a cold because no cause VOL. II. B develops it more frequently than sudden or prolonged exposure to a low temperature when the body is insufficiently protected. To understand how this happens, it will be necessary to remind the reader of the structure of the human skin. Every square inch of skin is perforated by several thousand openings, which are the apertures of corresponding glands by which the perspiration is separated from the blood. The quantity even of the insensible perspiration is very great, and it will surprise many to hear that, in the healthy state, it amounts to more than two pints in twenty-four hours. Under the influence of exercise or of unusual heat, Turkish bath, when perspiration drops from the body, it is, of course, considerably greater. The skin, owing to its structure, possesses a contractile power in a high degree. such as that of the Cold contracts almost all substances, and when the skin is exposed to its influence the contraction becomes visible to the eye, and the appearance it presents is called goose-skin, from its resemblance to the natural condition of the skin of the goose. Occasionally the effect of the contraction is to close rigidly the perspiratory pores, by which the escape of the secretion is obstructed. This, so far as we know, is the essential cause of what we call a cold. It seems that the fluid, having been checked in its natural outpour, is diverted |