436 



Prof. Burdon- Sanderson on the 



[Dec. 14, 



or when one or two points in the natural or artificial longitudinal section 

 so connected are at an equal distance from the central transverse section." 



The purpose of the present note is to put on record observations 

 which prove 



(1) That the unmutilated gastrocnemius muscle of the frog possesses 

 electromotive properties which have not before been correctly described ; 



(2) That iu the " muscle-cylinder " of Du Bois-Eeymond, the electro- 

 motive phenomena are dependent on and determined by those of the 

 muscle, and exhibit electrical properties which, in many important respects, 

 are inconsistent with the " law ; " 



(3) That the electrical change consequent on excitation, and termed 

 by Du Bois " negative variation," in like manner possesses characters 

 different from those assigned to it by him ; 



(4) That it is not true, as averred by Professor Hermann, that the 

 electrical state of muscle becomes negative during contraction as com- 

 pared with that of muscle at rest. On the contrary, the contracting parts 

 become positive. 



The following statements refer to the gastrocnemius muscle of the 

 frog. 



1. When one terminal of the Lippmann's capillary electrometer (de- 

 scribed in a previous paper by Mr. Page and myself) is connected by 

 a suitable electrode (to be called the fixed electrode) with the surface of 

 the back of a previously decapitated and pithed frog, and the other (the 

 movable electrode) with the surface of the gastrocnemius muscle at a 

 distance of from two to five millims. from the upper end, it is found 

 that the position of the mercurial column is nearly unaltered, indicating 

 that there is no, or only a slight, difference of potential between the two 

 surfaces thus compared. If the potential of the surface of the muscle 

 be positive, the neutral point can be found by shifting the electrode 

 further down ; if negative, by shifting it further up. 



2. If now the movable electrode is gradually shoved down the surface 

 of the muscle without breaking contact, the mercury alters its position 

 so as to indicate greater and greater negativity of the muscular surface, 

 until at last a point is reached near the tendon beyond which the surface 

 again becomes positive, the positivity increasing as the tendon is ap- 

 proached. 



3. If, the fixed contact remaining unaltered, the points already inves- 

 tigated are compared with other parts of the muscle, it is found that, 

 as a rule, (a) any two points equidistant from the origin of the muscle 

 exhibit the same potential, and (6) that the ends of the muscle exhibit 

 potentials which are identical with the potentials of the inactive tissues 

 {e.g. subcutaneous cellular tissue, bone, &c) in the neighbourhood, this 

 being true both as regards the insertion (tendon) and the origin of the 

 muscle. 



