372 
PEOrESSOE MATTEUCCI’S ELECTEO-PHYSIOLOGICAL EESEAECHES. 
rigorously those differences of this power which have led me to ground the explanation of 
the electro-physiological phenomena which take place on the opening of the chcuit on 
a fundamental physical fact. 
The arrangement which I have for a long time adopted in the study of these pheno- 
mena is well known, and has been described in several works on physics and physiology. 
This arrangement consists of a frog prepared after the usual manner of Galvaxi, and 
then cut in half at the symphysis of the pelvis. If a continuous current is passed from 
one limb to another for fifteen, twenty, or thirty seconds, according to the force of the 
current, it is knovm that the opening of the circuit is accompanied by \dolent contractions 
of the limb traversed by the inverse current. These contractions depend, as I showed 
many years ago *, on a particular state of the nerve ; and in fact the contractions ai’e 
obtained and continue when the circuit is interrupted by cutting the nerve near the spine, 
but they are no longer produced if the nerve is cut near its insertion in the muscles of 
the leg. 
My object in this memoir has been to prove that the particular state of the nerve above 
described consists of secondary electromotor power, that is, in a well-known physical 
phenomenon. 
I complete this demonstration by a very simple experiment. After havurg passed a 
current through two lumbar nerves of a fowl in the way already described, I lay the nerve 
of a galvanoscopic frog on different points of these nerves, precisely at the instant in which 
I open the circuit : I employ several galvanoscopic frogs in order to test with their nerves 
different points of the nerves of the fowl, and I also vary the direction of the nerves of 
the galvanoscopic frogs upon the nerves of the fowl. The instant that I open the circuit, 
the galvanoscopic frogs contract ; these contractions are also produced on touching the 
nerves of the fowl with the galvanoscopic frogs some instants after the opening of the 
circuit. Thus the secondary current, the existence of which is demonstrated by the 
galvanometer, and which is direct for the nerve that has been traversed by the inverse 
current, is also demonstrated by the contractions of the galvanoscopic frog : this direction 
of the secondary cuivent explains, according to the known laws of electro-physiology, the 
effects produced by it on the opening of the circuit. 
The differences of electromotor power found in various points of the electrolysed 
nerve, the prevalence of this power in the portions of the nerve near the positive elec- 
trode, very probably also the different degree of this secondary electromotor power in 
the various strata which compose the interior and the envelope of the nerve, explain 
sufficiently the secondary current which takes place in the nerve at the opening of the 
circuit, and which is direct and most intense in the nerve which has already been 
traversed by the inverse curr’ent in proximity to the positive electrode. 
In conclusion, in order to explain the physiological effects which accomparry the 
opening of a circuit, we must henceforth recur to the secondary electromotor power 
which is developed in nerves, and to the laws of this phenomerron. 
* Electro-Physiological Eesearches, Eifth Series, Part II. — Phil. Trans, for 1847, pp. 235, 236. 
