MUSCLE-FORCE. 67 



muscle of double thickness therefore possesses double 

 force. It is usual, therefore, to refer the force to units 

 of diameter of the muscle, by dividing the force by the 

 diameter of the muscle, and thus to calculate the force 

 of a muscle of 1 square centimetre diameter. 1 It has 

 been found that in the muscles of the frog the force, 

 for a diameter of 1 centimetre, is about 2-8 to 3 kilo- 

 grammes ; that is to say, a muscle of 1 centimetre in 

 diameter can attain a maximum tendency to contraction 

 which a weight of 3 kilogrammes is capable of resist- 

 ing. This value of the force reduced to units of dia- 

 meter is called the absolute force of a muscle. 



6. An attempt has been made to determine the ab- 

 solute muscular force in the case of man also. Edward 

 Weber first tried to do this by an ingenious method. 

 The muscles of the calf were chosen for the experiment. 

 On standing upright and contracting these, the heels, 

 and at the same time the whole body, are raised from 

 the ground. Gymnasts call this balancing. The whole 

 force of the calf-muscles of both legs is therefore greater 

 than the weight of the body. If the body is weighted, 

 a limit is reached at which it is no longer possible to 

 balance. The total weight of the body together with 

 that of all the weights applied, therefore, equals the 

 force of the muscles of the calf; but in calculating 

 this, however, attention must be paid to the fact that 

 the force and the burden do not act on the same lever, 



1 The following method, adopted by Ed. Weber, is used to de- 

 termine the diameter. The weight of the muscle, which is found 

 by the use of scales, is multiplied together with the specific weight 

 of the muscle-substance, the result being the volume of the muscle. 

 The length of the muscle is then measured, and the volume is 

 divided by the length, which gives the diameter. 



