142 
PEOFESSOE MATTEIJCCI’S ELECTEO-PHTSIOLOG-ICAL EESEAECHES. 
voltaic electromotor and that of the muscular electromotor, it is not impossible to con- 
ceive that the change of form which takes place in the muscle in contraction may be 
momentarily followed by the inversion of the current in the exterior arc. Neither would 
examples be wanting, taken from certain cases of electro-dynamic induction and also of 
voltaic circuits, in which this inversion of the current can be obtained by change in the 
form or in the relative distance of different parts of the circuit. But this is a new field 
of inquiry which cannot be given up to simply hypothetical views ; let us be satisfied 
with having proved that muscular contraction is accompanied by an electric discharge. 
In the second part of these Researches we shall show that an augmentation in the 
chemical phenomena of muscular respu'ation takes place in the act of contraction. 
Notwithstanding our present ignorance of the form of the electromotive element of 
muscle, we may therefore admit that the development of muscular electricity is most 
probably due to the chemical actions belonging to lining muscles. 
§ 4. We shall now speak, in the last place, of the mechanical efiects of muscular con- 
traction, limiting ourselves to experiments on the frog, because in this case orrly it is 
possible to make the research with a certain degree of exactitude, and becairse after 
having determined the mechanical effect for a frog, we shall be able to compare the 
effective work of a muscular contraction -with the ivork which we shall call theoretical. 
accordmg to the principles of the dynamic theory of heat. 
This research should be made on a single muscle, and not on the whole system of 
nruscles, as in arr errtire frog, because in the latter case the opposite effects of these 
muscles neutrahze themselves almost completely. I therefore errrployed the gastrocne- 
rrrius of a frog to which a small weight was attached, and which was made to contract 
by the passage of an electric currerrt. The object of the experiment is to determine the 
height to which this weight is raised in the act of contraction ; this I did by means of 
the dynamometer described hr the Fourth Series of my Electro-physiological Researches*. 
Among the experiments published by M. Helmholtz in his very important memou* on 
the velocity of the propagatiorr of rrervous power, there are several which might have 
served our pm'pose, if the weights attached to the muscles had not been too great ; for 
the comparison we propose requires the determinatiorr of the mecharrical work of the 
contraction of a muscle in raising its own weight only. Neither cordd we dedirce from 
the numbers found by M. Helmholtz, the muscular work in the case of nrrrscles to 
which a small weight is fixed, because it is known and admitted, accordirrg to the expe- 
riments of ScHWANH, that the quantity of work produced by a muscrrlar contraction 
increases, to a certairr limit, with the weight which stretches the muscle arrd which that 
muscle raises : this singular property of the muscular engiire has necessarily the effect of 
weakening more rapidly the contractile power of the muscle. 
The medium result of a great number of my experimerrts has beerr, that the contractiorr 
of a gastrocrremius which weighs 0-300 gr., stretched by a weight of lOgrs., raises that 
weight to the height of 1-412 mm. The mechanical work of a corrtractiorr of a gastro- 
crremius is therefore expressed by 0-00001457 kilogramrrre metres. This rrumber being 
* PhilosopHcal Transactions, Part IV. 1846. 
