

THE MUSCULAR CURRENT. 141 



is the so-called total current observed by Nobili. It is remarkable 

 that the direction of the total current in the Mammalia has the reverse 

 direction, i. e., from the head downwards. 



It is further stated by Budge that, in the sartorius muscle of the 

 frog, he found two currents ; one, the so-called natural current, pass- 

 ing in the muscle, from its lower to its upper end, and the other, cor- 

 responding in all respects with that described by Du Bois-Reymond, 

 which he names the artificial current, and which he says is present in 

 muscles only after a transverse section has been made through them. 

 The natural current, being always in one direction, whilst the artifi- 

 cial currents pass within the muscle, from the cut ends to the equator, 

 it follows that the former strengthens the latter in the lower half, but 

 opposes and weakens them in the upper half of the muscle. Budge 

 enters into other details, which cannot here be described. The subject 

 is yet open to much further inquiry. 



Portions of nerve, as we shall hereafter see, exhibit precisely similar 

 currents to those found in muscle, and these follow the same directions, 

 though they are weaker and more difficult of detection. So likewise 

 pieces of brain and spinal cord, give similar currents. Other parts, 

 such as the lungs, liver, and kidneys, offer either very slight or no 

 currents. In the frog's skin a current is developed, which is opposite 

 to that of the muscle ; for the section of the skin is positive, 'whilst 

 the surface is negative. 



The exact cause of the electric currents, present in living muscular 

 and other tissues, is not understood. They are doubtless, in some 

 way, connected with the constant molecular chemical changes of com- 

 bustion or oxidation, which occur in the nutrition of the living tissues, 

 with those incessant changes, indeed, which are characteristic of life, 

 and without which there is no life. But it is unknown whether such 

 chemical changes are the consequences of the electric currents, i. e., 

 are electrolytic ; or whether, as this seems more probable, the cur- 

 rents themselves are the necessary accompaniments of the chemical 

 changes. The nutritive molecular changes are doubtless more active 

 in muscle than in nerve, and probably more so in nerves than in the 

 skin ; the strength of the electric currents obeys the same order. It 

 is possible also that the nutritive changes are more active on the sur- 

 face or sides of the fibres than at their centres or cut ends when they 

 are divided, i. e., that they are more active on the surface of the fibres 

 which is found to be positive, than on the parts which are negative. 



The electrical current proper to, and constant in, healthy quiescent 

 muscle, or the normal muscular current, is evidently disturbed by the 

 contraction of the muscle. It was said by Matteuci to be reduced to 

 zero, or even to be reversed in direction ; but by Du Bois-Reymond it 

 is considered merely to be diminished, the needle being first deflected, 

 in an opposite direction, when the piece of muscle experimented on is 

 made to contract, but ultimately being merely less deflected than when 

 the muscle is at rest. This diminution of the muscular current takes 

 place all the same, whether the muscle be excited to contract by means 

 of a direct stimulus, or by means of a stimulus applied indirectly 

 through the motor nerve ; nor does the nature of the stimulus, whether 



