296 ELECTRO-PHYSIOLOGY. 



But if we employ a very strong discharge, the muscle remains contracted and 

 shortened for several minutes, and sometimes permanently. 



I shall here only add that, operating on a jii-epared frog in the manner which 

 I have described, and using, for the purpose of closing the circuit, a v,^heel with 

 teeth, part of metal and part of wood, we are able, by causing the wheel to re- 

 volve, to produce in extremely rapid alternation the passage of the current and 

 its interruption in the frog. This will then be seen to contract many times in 

 succession : if the wheel turns rapidly, that is, if the passages and interruptions 

 of the current are numerous and at short intervals, the frog remains contracted 

 and rigid ; if the wheel turns slowly, the contractions are distinct, but diminish 

 in intensity and presently cease. If we would renew the contractions, it is 

 necessary to leave the muscle in repose for some seconds. 



After having thus shown the best means for experimenting on the physio- 

 logical effects of the electric current, we should proceed to state the laws of 

 those phenomena, which will be done in the following lecture. 



Lecture II. — General facts of electro-physiology. — The physiological effects of electricity 

 depend on the variations of the electrical state. — Quantity of zinc or of electricity extremely 

 small in order to produce excitation of the nerve. — Principle of the preservation of living 

 forces. — Mechanical theory of heat. — Application to electro-physiology. — Electricity excites 

 the nerve, and the excited nerve occasions the chemical action of the muscular respiration. — 

 Electricity acts as the spark which kindles a mass of powder. 



In the first lecture I endeavored to define with exactness the phenomena 

 which pertain to electro-physiology, and to distinguish them from others attri- 

 buted to the electricity of vegetables and animals solely through the imper- 

 fection of our knowledge. With this view different examples were adduced in 

 which electricity produces in the living organism effects dependent either on 

 electro-chemical action or on known physical properties, and hence, independent 

 of the condition of life and of orgauiaation properly so called. We have seen 

 that the principal effect of electricity on animals consists in the shock — -that is, 

 in the paiij and muscular contraction, which the discharge or electric current ex- 

 cites in traversing the muscles or nerves of an animal either alive or recently 

 killed. And in order to observe more precisely this electro-physiological effect, 

 I have proposed dynamometers suitable for measuring the muscular action, and 

 described the manner of operating with them. We will now proceed to consider 

 the laws of electro-physiological phenomena, commencing with an attempt to 

 investigate their nature. 



Whenever a Leyden jar is discharged by a metallic arc or any liquid con- 

 ductor, and when with one of these arcs the circuit of a battery is closed, tho 

 different physical or chemical phenomena which are produced depend on the 

 time and on the quantity of electricity which circulates, and which is the cause 

 of those phenomena. Thus, if the current passes through the solution of sul- 

 phuric acid of a galvanometer and is constant, the quantity of water which is 

 decomposed, and the quantity of zinc which is oxidized in the battery, are 

 proportional -to the time — that is, to the quantity of electricity which passes. 

 And if the circuit instead of being constantly closed be alternately cl>)Sed and 

 opened by means of one of the common wheels of interruption having metallic 

 teeth of the same length with that of the isolating intervals, it will be found that 

 in the circuit constantly closed and in that interrupted the quantity of water 

 decomposed in the same time will be in the ratio of 1 : i. The calefaction of 

 the conductors traversed by the current or discharge depends also on the quan- 

 tity of electricity in a unit of time — that is, on the intensity of the current; and 

 the same may be said of the action which the voltaic conductor exerts on the 

 magnetic needle and of the property of magnetizing soft iron. 



