50 PHYSIOLOGY CHAP. 



the body produces rapid exhaustion on the ergograph, even if the 

 curve is obtained by electrical excitation. 



(d) Ergograph work may alter the elasticity of the muscle, 

 increasing or diminishing it ; in certain 'individuals it may excite 

 contracture, which is the more readily produced in proportion with 

 the strength and frequency of the stimulus, and the weight the 

 muscle has to raise. 



The ergograph curve depends on the combined effects of 

 fatigue of the nerve-centres and fatigue of the muscle, though the 

 latter always predominates. " The characteristic phenomena," 

 Mosso writes, " are peripheral, since the muscle exhibits its char- 

 acteristic fatigue curve even with artificial stimulation. ... It is 

 not the will nor the nerves, but the muscle that is weakened after 

 arduous brain-work." 



Maggiora subsequently brought out the great importance of 

 the varying conditions under which external mechanical work is 

 performed on the ergograph : 



(a) There is a certain weight which elicits the maximum of 

 utility ; with weights below a certain value, no sign of fatigue is 

 perceptible. 



(6) With every load, the slower the rhythm of contraction the 

 more external work can be performed, and the more the onset of 

 fatigue is delayed. For any given weight there is a rate at which 

 the contractions can proceed for a long time with no trace of 

 fatigue. 



(c) If a muscle is contracting at a given rate slow enough to 

 allow of its complete recovery at each contraction, and the load is 

 then doubled, it is not sufficient to reduce the rate to half its 

 original frequency in order to obtain the same yield of mechanical 

 work from the muscle. 



(d) The interval which must elapse between two ergo- 

 graphic curves in order to obtain normal fatigue curves during 

 the whole day is from 1J to 2 hours. The weight of the load is a 

 matter of indifference between certain limits (2-4 kgrms.). 



(e) The work performed by a muscle that is already fatigued is 

 far more injurious to that muscle than a greater amount of work 

 performed under normal conditions. 



In these studies Mosso, Maggiora, and other investigators, in 

 calculating the work effected by the muscle, neglected the end 

 part of the tracing which consists of low, long-drawn-out con- 

 tractions. Lombard (1890) investigated this terminal phase, 

 and discovered that when the ergogram appeared to stop, it 

 usually continues as a new series of contractions, in which the 

 rise and fall of the curve were approximately regular. According 

 to Lombard these periods are only to be seen in the voluntary 

 ergogram, and are due to spinal fatigue. 



Owing to the ease with which the ergograph can be used it is 



