CH. XI.-] 



MUSCULAR WORK. 



137 



In the diagram (fig. 158) the figures along the base line represent 

 grammes, and the figures along the vertical line represent milli- 

 metres. The work done as indicated by the first line is 10 X 5 = 50 

 gramme-millimetres, the next 20x6 = 120 gramme-millimetres, 



Fig. 158. Diagram to show the mode of measuring muscle work. (M'Kendrick.) 



and so on, while the last on the right, 100X3 = 300 gramme- 

 millimetres. It is thus seen that the height of a muscle curve is 

 no measure of the work done by the muscle unless the weight 

 lifted is taken into account as well. 



The following figures are taken from an actual experiment done 

 with the frog's gastrocnemius (Weber) : 



The work increases with the weight tip to a certain maximum, 

 after which a diminution occurs, more or less rapidly, according 

 as the muscle is fatigued. 



Similar experiments have been made in human beings, weights 

 being lifted by the 

 calf muscles, or elbow 

 muscles, leverage being 

 allowed for. In the 

 higher animals the 

 energy so obtained 

 compared with the 

 frog is about twice as 

 great for the same 



volume of muscular p^. I59 ._Dynamometer. 



tissue. 



Fig. 159 represents a common form of dynamometer for 

 clinical use, employed in testing the muscles of the arms and 



