70 PHYSIOLOGY OF MUSCLES AND NERVES. 



this energy during each instant in the form of increase 

 in speed which it imparts to its lower end and to the 

 slight weight attached to the latter. "We may now 

 raise the question as to the amount of force which the 

 muscle when it has already accomplished part, say one 

 half, of its contraction, can still evolve. Schwann, who 

 first raised the question, fastened a muscle to one end 

 of the beam of a scale and attached weights to the 

 other end, but supported this end in such a way that 

 the muscle was not extended. He was thus able to 

 determine the force of the muscle in the same way as 

 was described above with the apparatus shown in fig. 20, 

 which depends on exactly the same principle. L. Her- • 

 mann repeated Schwann's experiment with this appa- 

 ratus, which is more convenient for the purpose now 

 under discussion. The unweighted, or, at least, \ery 

 slightly weighted, muscle having been inserted in the 

 apparatus as accurately as possible, so that the platinum 

 point jp just rests on the plate, the muscular force is 

 determined in the way described above (^see pp. 65, 67). 

 The vice which carries the muscle is then lowered to a 

 certain definite extent, say 1 mm. If the muscle is 

 then irritated it can become shorter by 1 mm. before 

 it pulls the lever /i ; if it becomes yet shorter it must 

 raise the lever with the weights attached to it. The 

 weififht which it can still lift after it has become shorter 

 by 1 mm. may thus be found. The muscle-vice is then 

 again lowered — and this is again and again repeated. 

 A series of weight-values is thus obtained which corre- 

 spond with the force of the muscle during the different 

 stages of its contraction. The result of the experiment 

 is to show that the force of the muscle decreases, slowly 

 at the commencement of contraction, but afterwards 



