FATiaUE 5G1 



aeiduisis is present, c. g., uncompensated cardiac defects, severe anemia, 

 gas poisoning. 



FATIGUE 



The symptoms of fatigue, whether general or local, seem to be due 

 to an intoxication with the products of the excessive metabolic activ- 

 ity, and part of the symptoms, at least, seem to be due to acid intox- 

 ication. Among the metabolic products of muscular activity are 

 known to be creatin, creatinin, sarcolactic acid, and carbon dioxide. 

 The amount of acid developed in an active muscle is quite consider- 

 able, and when the activity is violent or prolonged the sarcolactic 

 acid accumulates, being formed faster than it can be removed. Part 

 of the acidity of the muscle is due, however, not to the sarcolactic 

 acid itself, but to monopotassium phosphate (KHoPO^), which is 

 formed by the action of the sarcolactic acid upon the dipotassium 

 phosphate present in the blood and muscle. The effect of these 

 various substances upon muscular fatigue has been studied experi- 

 mentally, and while the creatin seems not to be a " fatigue substance, ' ' 

 sarcolactic acid, monopotassium phosphate, potassium sarcolactate, 

 and carbon dioxide all cause muscle tissue to react to stimuli in the 

 same way that a fatigued muscle does (Lee).*"^ 



It is quite probable that the muscular weakness of diabetics, and 

 the exhaustion associated with many conditions in which organic 

 acids appear in the urine in abnormal quantities, depend, at least in 

 part, upon the effect of these acids upon the muscle tissue, for Lee 

 found that |8-oxybutyric acid causes the same fatigue reaction in mus- 

 cles as does sarcolactic acid. Furthermore, sarcolactic acid itself 

 often appears in the urine in these conditions. It may be added that 

 in fatigued animals the alkalinity of the blood (by titration) has been 

 found decreased (Geppert and Zuntz), and the proportion of the 

 urinary nitrogen that appears in other combinations than urea is 

 increased (Poehl).'^^ 



The "Toxins" of Fatigue. — In extreme exhaustion the evidences 

 of a general intoxication often become severe, so that the condition 

 may resemble an acute febrile disease and last for several days. It 

 seems very probable that substances more toxic than the above-men- 

 tioned acids are involved. Weichardt '- claims to have demonstrated 

 as produced by muscular fatigue a toxic substance, which in structure 

 resembles the bacterial toxins, called by him kenotoxin,'^-"' and against 

 which an antitoxin may be obtained. This toxic material is, he be- 

 lieves, formed from the protein molecule in the first stages of its de- 



60 Jour. Amer. Med. Assoc, 1906 (46), 1401; where is given a complete review 

 of the subject of fatigue, with tiie literature. 



eiDeut. med. Woch., 1001 (27), 706. 



«2 "Ueber Enniidungsstoffe," Enke, Stuttgart, 1012; Kolle and Wassermann's 

 Handbuch, 1013 (2), 1400. 



02a See Weichardt and Schwenk, Zeit. phvsiol. Chem.. 191.3 (83), 381. 

 36 



