56 PHYSIOLOGY CHAP. 



(/) The will as a psychical factor has no influence on the fall 

 of the curve with a constant load. Directly the load is adjusted 

 the tracing is prolonged by an unlimited number of contractions 

 with a considerable production of work. All other hypotheses are 

 superfluous, on which the functional incapacity which appears in 

 the ergograph curve only with the constant load has been 

 explained by assuming a sort of antagonism between the height 

 and the number of the contractions. 



(g) In order to elicit the whole work of which a muscle is 

 capable, in regard both to time and to amount, care must be taken 

 that the muscle is always engaged in maximal work. At whatever 

 load the work begins, the time necessary for attaining a constant 

 level is always the same. Still the muscle working under the 

 influence of the will with sub-maximal loads economises part of 

 the materials at its disposal, and may accumulate a fresh supply. 



(A) Given uniform conditions, the value of the initial maximal 

 load is constant in the same person on different days, and the 

 height of the contractions varies but little. The work curves 

 vary very slightly in the amount of work that can be obtained 

 with the initial maximal load, the terminal maximal load, and, 

 lastly, the total amount of work. 



(i) Fasting does not perceptibly alter the value of the initial 

 maximal load, but it accelerates the fall of the curve, and lowers 

 the value of the terminal maximal load considerably. Practice 

 and training, on the contrary, render the muscle capable of accom- 

 plishing much more work. After practice the initial maximal 

 load increases within limits, while the value of the terminal 

 maximal load increases from day to day, without, however, delaying 

 the fall of the curve to the constant level. 



(&) If the work is begun with the maximal terminal load 

 as determined by the previous experiments, the ergograph curve 

 forms a horizontal line. From this we must not conclude that 

 work under these conditions produces no appreciable fatigue in 

 the nerve-muscle apparatus. Fatigue, according to Treves, can 

 be studied simultaneously with the production of external work, 

 by determining the manner in which the nervous energy 

 diminishes. This is represented by the product of a given weight 

 into the time in seconds for which the weight can be held up by 

 the voluntary tetanus, continued to exhaustion, of a given group 

 of muscles. The line indicating the alterations of nervous energy 

 falls much more rapidly than that showing the variations of 

 the maximal load, and is in a marked degree independent of the 

 production of external work. 



At the Fifth International Congress of Physiology at Turin 

 Treves proposed certain modifications of his original ergograph, 

 by which he was enabled to control these observations and to 

 extend his research to the flexor muscles of the fingers (Fig. 37). 



