202 KANSAS UNIVERSITY SCIENCE BULLETIN. 



results in a test that required only one minute. Bolton (3), 

 in fact, worked with the method in Kraeplin's laboratory, and 

 found marked variations which he ascribes to after-images, 

 tingling sensations and the varying sensibility of the neigh- 

 boring portions of the skin. These variations obscured any 

 possible evidence of fatigue after adding one hour or walking 

 two hours. Nevertheless, Griesbach (13), Wagner (44) and 

 Vannod (41) have obtained results which they are satisfied 

 show a definite increase in the spatial threshold of the skin 

 after work, principally after gymnastic exercise ; and in a 

 later investigation Griesbach (14) has not only considered 

 this a measure of fatigue, but he finds that, while the spatial 

 threshold for both sides of the body may be increased with 

 fatigue, the increase is greater on one side or the other, de- 

 pending on the nature of the exercise. Thus, for physical 

 exercise, he finds a decrease in sensitivity of the left side of 

 the body, or a decrease in discriminability of the right hemi- 

 sphere. The experiments were performed upon forty-six sol- 

 diers at six to seven o'clock in the morning. The soldiers then 

 marched several miles to their drill grounds and spent the 

 remainder of the time until ten o'clock in general gymnastic 

 exercise. The men were taken from the field, one at a time, 

 and again tested. The pulse rate was found to be much higher 

 and the average threshold value on the left side of the body 

 was greatly increased for every subject. The average in- 

 crease for the right side was only slight, and many subjects 

 showed decreases. 



The chemical products of fatigue are of particular interest 

 to our problem. The presence of sarcolactic acid and potassium 

 with fatigue easily leads to the assumption, as similar phe- 

 nomena did for Mosso (30), that their circulation in the blood 

 must cause general fatigue. It may be that some day the 

 physiologist can demonstrate the presence or absence of these 

 substances in the cerebral centers following muscular fatigue. 

 At present the experiments are confined to their effect upon 

 the muscles and motor fibers. As early as 1865 Ranke (33) 

 found that the injection of a small amount of lactic acid in- 

 creased and a larger amount decreased the irritability of an 

 isolated muscle. Recently these experiments have been re- 

 peated more extensively by Lee (21) and by Burridge (6). 

 By the introduction of fatigue substances in small amounts 



