t 243 ] 
XV. Electro-Physiological Researches. — Seventh and last Series. Upon the relation 
between the intensity of the Electric Current, and that of the corresponding 
physiological effect. By Signor Carlo Matteucci, Professor in the University 
of Pisa, fyc. fyc. Communicated by Michael Faraday, Esq., F.R.S., &;c. fife. 
Received May 20, — Read June 10, 1847. 
In bringing to a conclusion mv series of researches on electro-physiology, I shall 
dwell in the present memoir on such of them as have frequently engaged my atten- 
tion, and which I have lately again enlarged upon as bearing directly upon the highest, 
and I would even say, most physical point of the science of electro-physiology. 
We admit as clearly demonstrated by experiment that electro-magnetic, as well as 
electro-chemical action, give the measure of the electric current ; in other words, 
that different quantities of electricity produce chemical and magnetic effects propor- 
tional to these quantities. What then is the nature of this relation between the 
quantity of electricity and the contraction thereby excited, when transmitted through 
the nerve of an animal either living or killed as recently as possible ? In an early 
memoir, published three years ago in the Ann. de Chem. et de Phys., and in a com- 
munication which I had the honour of making to the British Association at York, I 
described my first experiments on this subject. Nevertheless I have always been 
desirous of being able to renew these experiments with far more perfect instruments 
than I possessed at that time. 
All the apparatus which I have employed were executed by M. Breguet with his 
accustomed skill and talent. The principal among them (Plate XIL fig. 1) has been 
already described in my Fourth Series. In the course of the present memoir I will 
give the description of the other instruments. 
The following is the general disposition of the experiment. A frog prepared rapidly 
is reduced to a thigh with the leg, the lumbar nerve, and a morsel of spinal marrow" . 
An electric current, or a discharge from the Leyden jar, is passed through a certain 
length of this nerve. The electro-physiological effect is the contraction of the limb, 
which at the expiration of a given time is raised to a certain height. Let a deter- 
mined quantity of electricity now be passed, then the half, a third, a fourth of that 
quantity, and so on, and a measure be taken of the corresponding electro-physiological 
effect; that is to say, of the height to which the limb is raised, and within what 
time. 
It will be seen from this that there is no difficulty in putting forward the subject 
of the research, but the practical difficulty is very great. It is needless to describe 
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