INTOXICATION OF FATIGUE oG9 



ial conditions of all sorts more or less acidosis is present, c. g., uncompensated 

 cardiac defects, severe anemia, gas poisoning, surgical or traumatic shock. 



FATIGUE" 



The symptoms of fatigue, whether general or local, soom to he due 

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

 it}', 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 accunmlates, 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 (KH2PO4), 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, hydroxybutyric acid, 

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

 same way that a fatigued muscle does (Lee^-). Presumably these 

 substances act chiefly by virtue of their carrying hydrogen ions, al- 

 though there is some evidence that the negative ions of lactic and oxy- 

 butyric acids and some positive ions, especially potassium, are capable 

 of producing certain fatigue phenomena (Scott). Indole, skatole and 

 phenol may also produce fatigue conditions. 



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 efTect of these acids upon the muscle tissue, for Lee 

 found that /3-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 

 urinarj^ nitrogen that appears in other combinations than urea is 

 increased (Poehl).^^ Fatigue in man causes an increased urinary 

 acidity. -^^^ 



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 



" Full bibliography by Spaeth, Jour. Indust. Hyg., 1919 (1), 22. 



1^ Jour. Amer. Med. Assoc, 1906 (46), 1491; where is given a complete review 

 of the subject of fatigue, with the literature. Also see Scott, Public Health Re- 

 ports, 1918 (33), 605. 



" Deut. med. Woch., 1901 (27), 796. 



13" Hastings, Public Health Rep., 1919 (34), 1682; Barach, .^ler. Jour. Med. 

 Sci.; 1920 (159), 398. 



