98 PRACTICAL PHYSIOLOGY 



drum and, with the muscle weighted only by the lever, describe an 

 abscissa line corresponding to the resting muscle. With the writing 

 point again at the beginning of this line, stimulate the muscle once 

 and, from the top of the ordinate so marked, draw another abscissa 

 line corresponding to the muscle when contracted. Rotate the drum 

 by hand, so that the writing point is now 5 mm. along the " resting " 

 abscissa line ; hang 20 grms. on to the lever and stimulate, so as to 

 record a second ordinate 5 mm. from the first. Repeat this process, 

 increasing the weight by an equal amount each time. In this way 

 Fig. 101 was produced. It is clear that the distance of the lowest 

 point of each ordinate below the " resting " abscissa line represents 



FIG. 101. Comparative extensibility of resting and contracted 

 gastrocnemius. 



Temp., 12 C. Magnification, 5. Figures represent actual weights in grms. II is the 

 " resting " and C the " contracted " abscissa line. (A.P.B.) 



the extension of the resting muscle by a given weight, and that the 

 distance of the top of the same ordinate below the " contracted" 

 abscissa line represents the extension, by the same weight, of the 

 muscle when contracted. If the lowest and then the highest 

 points of the ordinate are joined, two curved lines are produced 

 which represent respectively the curves of extension of resting and 

 contracted muscle (Fig. 101). It will be seen that the extensibility 

 of contracted muscle is absolutely greater, and increases more 

 rapidly, than that of resting muscle. Hence, if the observations 

 were carried far enough, the two curve lines would ultimately 

 cross ; this means that if a muscle were loaded by a weight greater 

 than it could lift, it would during its stimulation actually lengthen 



