96 THE HUMAN MOTOR 



From this table it is seen that the muscle of a fresh corpse 

 has a Young's modulus E 0-95, and a resistance to fracture 

 R of 40 grammes per square millimetre. All the values decrease 

 with age. Finally, the resistance to fractures is that of the mus- 

 cular matter., and its covering and the deformation is not, accord- 

 ing to Wertheim, absolutely elastic. It is partially persistent, 

 i.e., return to the original length is retarded ( 43). The muscle 

 of a corpse has therefore imperfect elasticity. 



Determinations made on the living have shown that the 

 muscular elasticity is less imperfect, if not absolutely perfect ; 

 but it is known that, under these conditions, tonicity intervenes, 

 and matter tends to retract itself. The retfactibility or the 

 contractability is not the elasticity ; it is the property peculiar 

 to muscle of being able to retract when acted upon by an external 

 stimulus. The contraction is said to be voluntary in the case of 

 the excitation being of direct nervous origin. Mosso ( l ) distin- 

 guishes between elasticity and tonicity by means of a special 

 instrument, the myotome, acting on the muscle of the calf. He 

 established, with Benedicenti, that the resistance to deformation 

 is greater that Young's modulus is higher in a muscle that is 

 contracted than in one that is in repose. Weiss and Petren ( 2 ) 

 found that this was also the case in the resistance to fracture : 

 for the " force of contraction " adds to the resistance and to the 

 cohesion of the muscular substances. By suppressing the nervous 

 action by means of " curare " (a poison acting on motive nerves) 

 the elasticity of the muscles becomes similar to that of a corpse. ( 8 ) 



The resistance to torsion, a subject on which there is little 

 information, is less in the contracted muscle than in the relaxed 

 muscle ( 4 ), this being the opposite of what takes place under 

 traction. But this point needs verification. The muscles 

 have their own resistance, and a resistance due to their tonicity, 

 and by their tendinous insertions on the skeleton, they consolidate 

 it and maintain its parts in relative fixity, thereby giving 

 form and support to the whole structure. It is they, so to speak, 

 which make a safe scaffold for the various parts of the skeleton. 



The following table, and fig. 105, show the principal elements 

 of the muscular system. 



f 1 ) A. Mosso et Benedicenti, Arch. Ital. BioL, vol. xxv., p. 379 and 385, 

 1896 ; vol. xxviii., p. 127. 



( 2 ) Weiss and Carvallo, Comptes Rendus Biol., 1899, p. 122 ; Petren, 

 Skand. Arch. f. PhysioL, 1899, p. 328, and 1902. 



( 8 ) Spiridon A. Dontas, Ve Congres de PhysioL, a Turin, Sept., 1901. 

 Borelli (De Motu Animalium, 1680) had already made this observation. 



( 4 ) Schenck (Pflueger's Arch., vol. Ixxix., p. 342 ; Ixxxi., p. 583, 1900) ; 

 Kaiser (Centralblatt f. PhysioL, vol. xiv., p. 1 and 363, 1900). 



