DOCKERAY : PHYSICAL FATIGUE AND MENTAL EFFICIENCY. 199 



Mosso considers this difference to indicate merely different 

 types of individuals. Mental work causes not only fatigue 

 but a heightened emotional state, which endures longer with 

 one class than with the other. This heightened emotion 

 causes the greater muscular activity in some individuals. 

 As an explanation of the fact that mental work does have an 

 influence on the ergographic tracings he suggests two possi- 

 bilities: (1) The muscles might cede a part of their nutri- 

 ment to the nervous elements, as in fasting. But the muscles 

 rapidly recover after the fast is broken, while the weakness 

 known as fatigue requires time and sleep. (2) There is a 

 fatigue product generated which circulates in the blood and 

 makes fatigue general. This he demonstrated by the trans- 

 fusion of blood from a dog that had been kept running for 

 several hours into a dog that had rested for the same period. 

 The second dog showed all the signs of fatigue manifested by 

 the first dog. The work of Mosso has been somewhat criti- 

 cized by later investigators. The amount of physical exercise 

 involved in lecturing is a very important factor which no 

 doubt would affect the ergographic results, but which he neg- 

 lects to take into consideration. Also, his tests were not re- 

 peated sufficiently to secure a constant tendency under a 

 particular set of conditions. 



Lombard (24), working with a Mosso ergograph, found 

 that the voluntary contraction of the muscle gave rhythms 

 of contraction which still appeared when the muscle was 

 massaged. When the muscle was caused to contract by the 

 application of an electric stimulus until it could no longer 

 lift the weight, it would still respond to a voluntary stimulus. 

 Furthermore, when one finger was fatigued by voluntary con- 

 traction, another finger would give as great a curve as before. 

 He also found that in some individuals there are periods of 

 muscular ability and intervals of inability which succeed each 

 other more or less regularly after the first period of fatigue, 

 even though the will is applied uniformly at the maximum 

 throughout the experiment. These later changes did not ap- 

 pear when the nerves or muscles were stimulated electrically. 

 He concluded that while the fatigue from voluntary contrac- 

 tion must be of central origin, it must lie between the "will 

 center" and the centrifugal nerves. The central origin of 

 fatigue was also evidenced by Joteyko's (17) ergographic 



