MUSCULAR WORK. 135 



through a less distance, the work done by the muscle goes 

 on increasing, for the bigger weight lifted more than com- 

 pensates for the less distance through which it is raised. 

 For example, if the above muscle were loaded with fifty 

 grams it would maybe lift that weight only 1.5 millime- 

 ters, but it would then do seventy-five gram-millimeters 

 -of work, which is more than when it lifted ten grams six 

 millimeters. A load is, however, at last reached with 

 which the muscle does less work, the lift becoming very 

 little indeed, until at last the weight becomes so great that 

 the muscle cannot lift it all and so docs no work when 

 stimulated. Starting then from the time when the muscle 

 carried no load and did no work, we pass with increasing 

 weights, through phases in which it does more and more 

 work, until with one particular load it docs the greatest 

 amount possible to it with that stimulus: after ihat, with 

 increasing loads less work is done, until finally a load is 

 readied with which the muscle again does no work. What 

 is true of one muscle is of course true of all, and what is 

 true of work done against gravity is true of all muscular 

 work, so that there is one precise load with which a beast 

 of burden or a man can do the greatest possible amount of 

 work in a day. With a lighter or heavier load the distance 

 through which it can be moved will be more or less, but 

 the actual work done always less. In the living Body, how- 

 over, the working of the muscles depends so much on other 

 things, as the due action of the circulatory and respiratory 

 systems and the nervous energy or "grit" (upon which 

 the stimulation of the muscles depends) of the individual 

 man or beast, that the greatest amount of work obtainable 

 is not a simple mechanical problem as it is with the excised 

 muscle. 



Influence of the Form of the Muscle on its Working 

 Power. The amount of work that any muscle can do de- 

 pends of course largely upon its physiological state; a 

 healthy well-nourished muscle can do more than a dis- 

 eased or starved one; but allowing for such variations the 

 work which can be done by a muscle varies with its form. 

 The thicker the muscle, that is the greater the number of 



