THE CHEMISTRY OF MUSCLE. 



69 



develop movement. Regarding the means used in the muscle to 

 transform the original chemical or internal energy to mechanical 

 movement we have no or very little positive knowledge. Numer- 

 ous theories of a more or less figurative character have been pro- 

 posed. It has been suggested (Weber) that the muscular force is 

 essentially due to the elasticity of the muscle. It is known that the 

 elasticity of substances may change with conditions, and it is 

 assumed that after stimulation the physical condition of the muscle 

 is changed and that the increased elastic attraction between the 

 particles gives it the form of 

 the contracted muscle. Ac- 

 cording to others (Fick), the 

 mechanical contraction is a 

 direct result of an increased 

 chemical affinity, while others 

 (Miiller) find an explanation in 

 supposed electrical charges 

 upon the doubly refractive 

 particles of the muscle in conse- 

 quence of which there are de- 

 veloped electrical attractions 

 and repulsions at the different 

 poles. The most specific and 

 comprehensible hypothesis ad- 

 vanced is that formulated by 

 Engelmann.* This author has 

 shown that all contractile 

 tissues contain doubly refrac- 

 tive particles, that in the 

 striped muscle fiber these par- 

 ticles are arranged in discs, 

 the dim bands, with the singly 

 refracting material forming the 

 light bands on either side. Dur- 

 ing contraction it has been 

 shown that the material of this 

 latter structure is absorbed by the doubly refractive substance. 

 Engelmann has shown, moreover, that dead substances, which 

 contain doubly refractive particles, such as catgut, when soaked 

 with water will shorten upon heating and relax again upon cooling. 

 His explanation of the mechanics of contraction in brief is that 

 the chemical change brought about in the muscle liberates heat, 

 and that the effect of this heat upon the adjacent doubly refractive 



* Engelmann, "Ueber den Ursprung der Muskelkraft," Leipzig, 1893; 

 see also "Pfliiger's Archiv," 7, 155, 1873. 



Fig. 26. Engelmann's artificial muscle. 

 The artificial muscle is represented by the 

 catgut string, TO. This is surrounded by a 

 coil of platinum wire, w, through which an 

 electrical current may be sent. The catgut 

 is attached to a lever, h, whose fulcrum is at 

 c. The catgut is immersed in a beaker of 

 water at 50 to 55 C., and "stimulated" 

 by the sudden increase in temperature caused 

 by the passage of a current through the coil. 

 (After Engelmann.) 



