1876.] 



Electromotive Properties of Muscle, 



437 



4. If the tendon is divided and tlie muscle, remaining attached by its 

 origin, is separated from its other connexions, so that it is out of contact 

 \vith surrounding tissues, and in this state is reinvestigated, it is found 

 that the negativity increases from its origin towards the negative point, 

 and diminishes from that point towards the tendon in the same way as 

 before, the only change observable being that the absolute difference of 

 potential between that spot and the fixed contact is greater than before, 

 i. e. that all the other less differences are proportionally exaggerated. 



5. If the muscle is throw^n into tetanic contraction by faradization 

 of the sciatic nerve for a period of two seconds' duration, the excitation is 

 accompanied by an excursion of which the direction is positive, and which 

 attains its maximum during the second half of the period during which 

 the excitation lasts, beginning to decline immediately after its cessation. 

 The extent of the excursion is such as to indicate that the electromotive 

 force of the muscular tissue diminishes by about a third. This pheno- 

 menon is observed before as well as after separation of the muscle from 

 its connexions. 



6. If now the muscle is severed in its upper third by a cut transverse 

 to its axis, and again in the region of greatest negativity by a second 

 cross cut, a muscle-cylinder is obtained having the follo^'\ing properties, 

 viz. : — (1) The upijer cut surface is negative to the natural surface in its 

 neighbourhood, but positive to the more distant parts. Between these 

 parts an intermediate zone may manifestly be found where the tension 

 of the natural surface is equal to that of the upper cut surface. 



(2) As compared with any point of the natural surface in this zone 

 the lower cut surface is strongly negative ; any point of the natural sur- 

 face nearer the lower cut surface is also negative, its negativity increasing 

 with its distance from the zone ; and in like manner any point nearer the 

 upper cut surface is positi^-e, the more so the further it is from the 

 zone. 



(3) When the muscle-cyhnder is thrown into contraction by contact 

 with platinum wires in connexion with the ends of the secondary coil 

 of a Du Bois's induction-apparatus, excitatory variations are observed, 

 having the following characters : — a. If one terminal of the electrometer 

 is in connexion with the natural surface at a point equidistant from both 

 ends (Du Bois's equator), and the other wdth the upper cut surface, the 

 position of the mercurial column indicates that the cut surface is nega- 

 tive to the natural surface, i. e. the former to the latter. On excitation 

 the difference of tension between the two increases — i. e., in Du Bois's lan- 

 guage, a positive variation occurs, h. If the same part of the natural 

 surface is now compared with the lower cut surface, and the excitation 

 repeated, the difference of tension between the two is found to be in the 

 same direction as in the former case, but much greater. On excitation 

 it diminishes — ?'. in Du Bois's language, a negative variation occurs. 



7. Erem the foregoing facts as to the muscle-cylinder prepared in the 



