Page:Popular Science Monthly Volume 2.djvu/425

Rh animal heat; that is to say, it directs and in a manner oversees its production and diffusion according to the varying needs of the system. Every lesion or affection of this system reacts on the physiological processes, and particularly on the evolution of heat. By cutting the filament of the great sympathetic nerve on only one side of a rabbit's neck, Claude Bernard produced an elevation of temperature of several degrees on that side. The blood flows toward the point where the action of the nervous system is suspended under any influence whatever, bringing with it an increase of heating force. At a point where the reverse occurs, the vessels contract, and the temperature falls.

Imperfect nutrition and fasting act on the animal heat, but not directly. The organism keeps up to its normal degree of temperature till it has exhausted its reserved store of combustible substances. Then it cools slowly down to a much lower degree. Thus, a rabbit, starved by Chassat, showed the first day a warmth of 38° 4' (cent.); two days before its death, 38° 1'; the evening before, 37° 5'; and at the moment of death, 27°. By placing it in a warm medium the moment it was about to die, the apparent activity of its functions was restored for a little while; but the renewal is of brief duration: the anatomical elements have absolutely lost their spring.

The hand of an invalid, suffering from inflammation of the chest, or from an attack of fever, is burning; that of one affected by serious asthma, or by emphysema, is as cold to the touch as marble. This is because animal heat varies greatly in different pathological states. Sometimes it rises, sometimes it falls; and the morbid influence is scarcely ever compatible with the body's degree of normal temperature. In Hippocrates's time, when examination of the pulse was not yet practised, the increase of temperature was the only element in the commonest of maladies, fever. Galen defines it quite simply as an extraordinary heat (calor præternaturalis substantia febrium). The ancients did not err. It has been admitted and proved in our days, that the elevation of the animal heat is just the specific character of the febrile condition. On the one hand, there is never any fever when the temperature continues at the normal degree; on the other, the rapidity of the pulse may reach the utmost limits, without any febrile movement, as is seen in hysteria. Whenever the bodily heat exceeds 38° (cent.), it may be affirmed that there is fever; and, whenever it falls below 36°, there is what is termed algidity. So that the normal heat varies within the narrow range of scarcely two degrees. Beyond these limits, that is, above 38° and below 36°, the temperature points out some morbid trouble. In common intermittent fever, it rises two or three hours before the chill, reaches a maximum at the close of it, and then falls. Acute and decided inflammations, such as pneumonia, pleurisy, bronchitis, erysipelas, etc., are marked by a period of thirty-six hours, or about two days, during which the heat rises slowly to 41°. Toward the third day, this heat decreases, ready to reappear in