BY DR. MICHAEL FOSTER. 361 



Then place 10 grammes in the pan, or hang a 10 gramme 

 weight on the lever. The point of the lever will move down- 

 wards, describing a line of a certain length. This indicates 

 the amount of extension which the muscle has suffered in con- 

 sequence of being loaded with the 10 gramme weight. 



Remove the weight carefully ; the point of the lever will re- 

 turn to the point where it was before the weight was applied. 



The distance of the point of attachment of the muscle and 

 that of the point of the lever from the fulcrum being known, 

 the actual extension of the muscle with 10 grammes may be 

 calculated from the length of the line marked on the cylinder. 



"Muscle possesses very little elasticity (i. e., is very extensi- 

 ble} ; but that little is very perfect ; i. e., on withdrawal of the 

 extending force, the muscle returns very rapidly and com- 

 pletely to its previous length." 



Obs. II. Now move the recording surface till the lever point 

 stands at the mark 30; load the pan with 30, and proceed as 

 before. Repeat at 50, 100. 200, etc. Before trying the heavier 

 weights (300, 400), see that everything is secure, especially the 

 clamps on the femur and on the tendon. As a general rule, 

 the attachment of the muscle to the femur at last gives way. 



With the heavier weights it will be found that the muscle 

 returns after extra extension and upon removal of the weights 

 towards its former length, at first very quickly, and then more 

 and more slowty and that even after waiting for some minutes, 

 it does not regain its former length completely. 



This falling short of a complete return is due to exhaustion 

 (commencing death, see Obs. IV.). The student had better, 

 in one set of observations, start in each case from the point of 

 the ordinate to which the lever had returned after the previous 

 extension, but of course from the next point on the abscissa, 

 and in another set bring down the recording surface in each 

 case so that the lever may start afresh from the abscissa line. 

 The lever should be horizontal at the beginning of eacli trial. 

 The pan or weight should also be allowed to descend very 

 gradually and slowly, to avoid momentum. Where there is 

 no arrangement for keeping the recording point in a straight 

 line, a horizontal line drawn through the end of each curve will 

 cut off from a vertical line, drawn through the starting-point, 

 a line equal to the vertical distance traversed by the lever 

 point. 



If now the lines so obtained be examined, it will be found 

 that though with the greater weights there is greater extension, 

 yet the increase of extension caused by increase of weight gets 

 less and less. The extension increases not in direct propor- 

 tion to the weight, but with continually diminishing increments. 

 If a line be drawn through the points which in each case mark 

 the limit of extension, that line will not be a straight line as it 



