. General physiology; an outline of the science of life. STIMULI AND THEIR ACTIONS 467 also independently of the blood-current which biings in food-stuffs and takes out excretory matters, the factors which, in union with oxygen, are necessary to the restoration of irritability. If we turn from the phenomena of fatigue that are externally visible in the muscle itself to those that develop secondarily in the body as results of very strong muscular effort, we meet with certain facts which bring us a step farther in the knowledge of fatigue. If we observe the phenomena that develop in our body in
. General physiology; an outline of the science of life. STIMULI AND THEIR ACTIONS 467 also independently of the blood-current which biings in food-stuffs and takes out excretory matters, the factors which, in union with oxygen, are necessary to the restoration of irritability. If we turn from the phenomena of fatigue that are externally visible in the muscle itself to those that develop secondarily in the body as results of very strong muscular effort, we meet with certain facts which bring us a step farther in the knowledge of fatigue. If we observe the phenomena that develop in our body in the course of strong muscular effort, we notice first a considerable acceleration and deepening of the respiration. At the same time the frequency of the heart-beat becomes increased. The produc- tion of heat which is increased by the muscular activity, is essentially compensated reflexly by the outpouring of per- spiration, the evaporation of which lowers the temperature. If. Pig. 242.—Parotid of the rabbit. A^ During rest; the cell-nuclei are indented. B, After stimula- tion through the sympathetic ; the nuclei have become round. (After Heidenhain.) the activity has been very considerable, not rarely a slight fever appears, especially when the body has made no muscular effort for a considerable time previously. The temperature rises, there are attacks of shivering, and a certain increase in irritability of the central nervous system is noticeable. This fact is so well known that there is recognised a " gymnast's fever," which appears in gymnastic work after too strong exertion. This fever of fatigue is also very frequently observed after very exhausting mountain tours and after long riding. Among the subjective symptoms that manifest themselves as a result of very strong muscular exertion, the best known are excitement appearing during the stage of the fever, , in the evening after an exhaustive march, sleeplessness, lack of appetite, and intense muscle pains,
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