PEOFESSOE MATTETJCCI’S ELECTEO-PHTSIOLOaiCAL EESEAECHES. 
371 
by the current in a direction contrary to that of its ramification {inversely^ as it is called 
in electro-physiology) had acquired a stronger electromotor power than that acquired by 
a nerve traversed in the direction of its ramification. Naturally, owing to a difierence in 
the length, and consequently in the resistance of the nerve, this difierential current must 
be stronger when the experiment is made on the two halves of a nerve than on two entire 
ner\'es. The same result may be obtained with different arrangements of the experi- 
ment. One of these arrangements consists in taking rapidly from a fowl the two nerves 
of the thigh, and in disposing these nerves one after another as they were in the living 
animal, so that the cm'rent traverses the one in the same direction as the ramification, 
and the other in the opposite direction. After being traversed by the current, the nerves 
are put in opposition ; a differential current is determined by the nerve which, for the 
sake of brevity, we shall call inverse. 
Here, once for all, I observe that in making these comparative experiments it is neces- 
sary to have a galvanometer and a rheostat in the circuit, in order to obtain constantly 
the same pile-current. 
Another analogous way of performing this experiment is to employ a prepared animal 
such as is used in the electro-physiological experiment which demonstrates the infiuence 
exercised by the direction of a continuous current on the irritability of a nerve. As is 
well known, this preparation consists of the two limbs of an animal united by the two 
nerves of the thighs connected with a portion of the spine. The extremities of the limbs 
are immersed in water contained in two glasses, together with the electrodes of the pile ; 
and thus the cmTent goes from one limb to the other, traversing the two nerves, inversely 
in the nerve next the positive electrode, and directly in the other nerve, next the negative 
electrode. This experiment may be made on Ihing animals, that is, with the entire 
trunk, and on animals such as frogs, fowls, and rabbits recently killed, by prolonging the 
passage of the current from a few seconds to twenty or thirty minutes, according to its 
intensity. Both the nerves acquire a strong secondary polarity ; but the inverse nerve 
acquires a stronger secondaiy electromotor power than the direct, and in both neiwes 
the secondary electromotor power is greater in the portion near the positive electrode 
than in that which is near the negative electrode. 
The object of these researches was not, as we have said, to study the production of 
secondary electromotor power in nerves rather than in other porous and humid bodies 
of various structm'e and chemical composition. Under this pomt of view it is evident 
that the phenomenon is complex and its analysation difficult. In the present state of 
science, therefore, we are unable to account for the differences presented by a nerve in its 
different points, according to their proximity to one pole or the other, and according to 
the direction in which the neiwe is traversed by the current. It is possible that similar 
differences will present themselves in other bodies which are not organized, or taken from 
living animals. It is sufficient for my present object to have proved that the secondary 
electromotor power of a nerve requires for its development the integrity of structure of 
the nen e itself, but not the excitability of the living animal, and to have determined 
MDCCCLXI. 3 p 
