Kansas Academij of Science. Ill 



SOME CHEMICAL PRODUCTS OF PHYSICAL FATIGUE 



AND THEIR POSSIBLE EFFECT ON 



MENTAL EFFICIENCY. 



(Abstract.) 



F. C. DOCKEEAY. 



IN an article recently published in the Kansas University 

 Science Bulletin I have briefly reviewed the investigations 

 concerning the chemical products of physical fatigue. Lactic 

 acid, potassium salts and carbon dioxide have been shown by 

 investigators to be closely associated with decreased physical 

 activity. Injection of lactic acid, for example, into an isolated 

 muscle or into a normal rat produces the same effect that con- 

 tinued contraction or work would do. 



But a small amount of lactic acid does not have an effect pro- 

 portionate to a larger amount. On the contrary, a low concen- 

 tration of lactic acid, or potassium salts, produces increased 

 activity in the rat, and an isolated muscle shows a like aug- 

 menting effect by an increase in the height of the work curve. 

 As the concentration is increased the augmenting effect is re- 

 placed by decreased activity. 



In the investigation of the relation of physical fatigue to 

 mental efficiency, cited above, I have found similar phenomena. 

 A moderate amount of physical fatigue is followed by increased 

 mental ability, as evidenced by memory and attention tests. 

 Following greater physical fatigue, mental fatigue decreases, 

 if not immediately then soon after rest begins. It may be as- 

 sumed that these results are due either to the distraction 

 effects of the sensations of fatigue or to the presence of one or 

 more of the fatigue products in varying degrees. 



More recent experiments, as yet unfinished, bearing upon 

 the former theory seem to indicate that these effects can not 

 be entirely ascribed to distractions. The latter theory offers 

 an opportunity for further research. 



University of Kansas, Lawrence. 



12— Sci. Acad.— 2163 



