328 ELECTEO-PHYSIOLOGY. 



physics, and endeavor to tlirow some light on the mode of action of this electro- 

 motor. But first, and iu the interest indeed of this theoretical research, I must 

 state the laws of muscular electricity, that is, its relations with the physical and 

 physiological properties of the muscle. 



The first proposition relative to the physical condition of the muscle is the 

 following: The electro-motor power of the muscle is independent of the size of 

 the muscle itself, or of the magnitude of its transverse section, and is, on the other 

 hand, proportional to the length of the ynusclc. 



This proposition, as well as those which follow, is founded on experiments 

 very aptly performed upon the principle of opposition before mentioned. Thus, 

 for the first part of the proposition, it is sufficient to prepare a certain number 

 of half thighs of frogs, and to construct a double battery formed on one part of a 

 single half thigh, and on the other, of five or six elements, which are all superposed 

 in the same direction. From this double battery there is no differential current, 

 or one very slight, and m. the direction indifferently of a single element or of the 

 combined elements. The same result is verified by coHating the muscular ele- 

 ments of very different size with one another, unless it be found that in this 

 case the differential current is almost always in the direction of the thicker 

 muscle, the reason of which will be presently shown. 



We proceed in like manner to show that the muscular current is proportional 

 to the length of the muscle. A double and opposed battery formed of two half 

 thighs being prepared, after having ascertained the equality of these two ele- 

 ments, we execute with each of them a new transverse division parallel to the 

 first ; with this difference, that iu one of the elements the operation is restricted 

 to the removal of a very thin slj-atum, while in the other it should reduce the 

 element to not more than a third or fourth of the previous length. 'J'he battery is 

 then reconstructed, and we have now a differential current ia the direction of 

 the longer muscle. This result has also been realized with the gastrocnemian 

 and the long dorsal muscles of the rabbit. Hence Ave derive an explanation of 

 the observation made by Du-Bois Reymond regarding the current obtained by 

 touching two non-symmetrical points of the same transverse section. This current 

 indicates that the points of this section nearest to the centre act as the trans- 

 verse section, and stand in relation to points further from the centre as if these 

 last pertained to the surface of the muscle. The fibres of the centre are, in effect, 

 longer than the fibres situated near the edge of the transverse section, and 

 the resulting current is in conformity with the proposition above stated. 



Let us pass now to the physiological laws of the muscular current, and here 

 also, for sake of brevity, I shall state such well-established facts as we possess 

 in the form of propositions, 



First pn-oposition. — "The electro-motive force of the muscle in an animal 

 living or recently dead is greater in the mammifers and in birds than in fishes 

 and reptiles. This force rapidly diminishes after death, but in an inverse order 

 as regards the animal series, and still with great differences. The muscular 

 electricity varies, therefore, as the so-called muscular irritability." 



As this irritability is extinguished very rapidly in mammifers and birds, par- 

 ticularly in a detached muscle of the animal, it is necessary to operate with 

 great promptness iu order to demonstrate the first part of this proposition. 

 Having prepared, therefore, the half thigh of a frog, we rapidly detach a thigh 

 from a living bird, cut the thigh in half, remove the skin, and promptly form the 

 double battery with the opposed elements of the frog and the bird. In the 

 greater number of cases the differential current is in the direction of the bird. 

 If, after some moments, the battery be reconstructed, we shall see the diff(;rential 

 current arise iu the opposite direction, that is, in favor of the muscle of the frog. 

 Giulio liegnault, iu measuring with thermo-electric units the electro-motor 

 •powers of the muscle of the rabbit and of the frog, found that, iu the first mo- 



