"But what is the nature of this alteration? In this case, every clew to the solution of this question fails us. We know well, when the experiment is designedly prolonged, the blood grows black, as in _asphyxia_, (loss of pulse,) through the combination with it of carbonic acid, whose presence is opposed to the absorption of oxygen. But what relation is there between this chemical alteration of blood here and the modifications in composition it may undergo under the influence of instantaneous suppression, but not persistent, of the cutaneous exhalations and secretions? The experiments of Dr. Fourcault tend, on the whole, to explain this. His experiments discover the primitive form and almost the nature of the alteration the blood undergoes under the influence of the cessation of the functions of the skin. They demonstrate that under these conditions the regularity of the course of this fluid is disturbed--that it has a tendency to accumulate and stagnate within the internal organs: witness the abdominal pains so frequently consequent on the application of plasters upon the skin, and the congestions of the abdominal and pulmonary vascular systems met with almost always on opening animals which have been suffocated through tar or pitch plasters. "They prove, in fact, the thorough aptitude of impression of the nervous system to blood altered in its chemical properties, while they afford us an explication of the phenomena of depression, and muscular prostration, and weakness, which accompany the beginning of disease consecutive on the operation of cold. "How often do we put a stop to the ulterior development of disease by restoring the function of the skin by mere [dry] friction, putting on thick clothing, exposing to exciting fumigation, applying temporary revulsives in the shape of mustard poultices, administering diffusible stimuli made warm in drenches, trying every means to force the skin, and so tend, by the reëstablishment of its exhalent functions, to permit the elimination of blood saturated with carbonic matters opposed to the absorption by it of oxygen! "Do we not here perceive, so to express ourselves, the evil enter and depart through the skin? "M. Roche-Lubin gives an account of some lambs which were exposed, after being shorn, to a humid icy cold succeeding upon summer heat. These animals all died; and their post mortem examination disclosed nothing further than a blackened condition of blood throughout the whole circulating system, with stagnation in some organs, such as the liver, the spleen, or abdominal vascular system. "From the foregoing disclosures, which might be multiplied if there was need of it, we learn that the regularity or perversion of the functions of the skin exercises an all-powerful influence over the conservation or derangement of the health, and that very many diseases can be traced to no other origin than the interruption, more or less, of these functions."