Page:Popular Science Monthly Volume 2.djvu/429

Rh which, carrying the blood continually from the surface to the centre, bears heat also along with it, then at a given moment it falls into convulsions, the beating of its heart ceases, and it dies uttering a cry. By means of the thermometer it is noted that the temperature of the animal, in every case, is higher by four or five degrees (cent.) than the figure which represents the normal warmth. Thus at first the animal is excited, its functions seem to be performed with fresh vigor, very much as, in the first rays of April sunshine, the pulsations of life in all beings become more rapid; but this stimulus is only fleeting, and soon, when it reaches a certain degree, this heat gives place to the cold of death. Bernard carefully examined animals dying under these conditions, and the first phenomenon that struck him was the rapidity with which corpse-like rigidity came on. The heart grew suddenly insensible to any stimulus; effused spots appeared at several points on the skin. The heat fixed in coagulation the soft matter that composes the muscular fibres. These had the look of being struck with lightning. On the other hand, the arterial blood of the animal grew black, ill-supplied with oxygen, overloaded with carbonic acid, and assumed the look of venous blood. Yet in this state the blood has not lost its physiological properties, and under the influence of a new supply of oxygen can regain its normal state, and grow ruddy again. The heat, provided the degree be not too elevated, only promotes activity in sanguine combustion, without changing the blood. Nor does the nervous system either appear to suffer much. The element most deeply affected is muscle; heat is a poison of the muscular system, like sulpho-cyanuret of potassium, and the upas-antiar. It is the loss of the vital properties of this system, which, by bringing about rigidity of the muscles, then the stoppage of circulation, and consequently of respiration, is a necessary cause of death. This destruction of the contractile muscular fibre occurs toward 37° or 39° in cold-blooded animals, toward 43° or 44° in mammals, toward 46° or 48° in birds, that is, speaking generally, at a temperature five or six degrees higher than the natural temperature of the animal. Bernard calls attention to the fact that in no case is it allowable to suppose that life opposes a kind of resistance to the excessive heating; on the contrary, vital movement tends to quicken it, and that may be readily understood. The internal heat produced by the animal unites with the acquired heat, and the renewal of the blood, which is the condition of the heating, then occurs with much greater activity. Let us add that quite lately Demarquay applied this toxic action of heat on the muscles in the happiest manner, and without suspecting it. He cured patients suffering from those frightful muscular contractions which characterize tetanus, by subjecting them to the influence of caloric, and making them take very hot air-baths. The rise of temperature in the tetanized muscles was sufficient to modify them, and restore them to a healthy state. Here the poison worked a cure.