STIMULI AND THEIR ACTIONS 467 



also independently of the blood-current which brings 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 



FIG. 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, e.g., in the evening after an exhaustive march, sleeplessness, 

 lack of appetite, and intense muscle pains, which appear usually 

 upon the next day or even later. 



These phenomena together present an interesting complex of 

 symptoms, which remind the physician very strongly of the 



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