498 Drs. A. Fick and J. Wislicenus on the 



muscles as if work were being performed which did not undergo 

 this transformation. In order to make this point yet clearer, we 

 may take into consideration that the whole work of the ascent 

 only existed temporarily as work. On the following day the 

 result was reversed ; our bodies approached the centre of the 

 earth by as much as they had receded from it the day before, 

 and, in consequence, on the second day an amount of heat was 

 liberated equal to the amount of work previously performed. 

 The two parts of the action, which in this case were performed 

 on two separate days, take place in walking on level ground in 

 the space of a footstep. 



Let us observe, besides, that in an ascent it is not only those 

 muscles of the leg specially devoted to climbing which are ex- 

 erted, the arms, head, and trunk are continually in motion. For 

 all these movements force-generating processes are necessary, the 

 result of which cannot, however, figure in our total of work, but 

 must appear entirely in the form of heat, since all the mechani- 

 cal effects of these movements are immediately undone again. 

 If we raise an arm, we immediately let it drop again, &c. 



There was besides a large portion of our muscular system em- 

 ployed during the ascent, which was performing no external 

 work (not even temporary work, or mechanical effects immedi- 

 ately reversed), but which cannot be employed without the same 

 force-generating processes which render external work possible. 

 As long as we hold the body in an upright position, individual 

 groups of muscles (as, for instance, the muscles of the back, neck, 

 &c.) must be maintained in a state of continual tetanus in order to 

 prevent the body from collapsing. This point seems to have been 

 much misunderstood ; and we will therefore discuss it, shortly 

 but fundamentally. The reason of this misunderstanding is, 

 that in many treatises on the subject such employment of the 

 muscles is denominated " statical work," although there is really 

 no work when a tetanized muscle holds a burden in equilibrium. 

 It is only at the commencement of this condition, when the bur- 

 den is raised, that there is any work. We might therefore, in 

 order to correct this misunderstanding, and shortly to designate 

 the condition in question, propose the expression " statical acti- 

 vity." While the tetanized muscle is maintaining a burden in 

 equilibrium, it is certainly in an active state. As long as it sup- 

 ports the burden, the force-generating processes must be active 

 in it ; but the whole of the actual energy thereby produced must 

 necessarily be liberated in the form of heat ; for no work is really 

 performed. It may assist in comprehending this if we put be- 

 fore the reader a perfectly similar and more simple case. Let 

 us imagine a cylinder standing perpendicularly and closed at the 

 bottom ; it is filled with some kind of gas, and the whole is in 



