ELECTRICAL THEORY OF MUSCULAR CONTRACTION. 407 



that electrical, chemical, and mechanical irritants are, in this respect, 

 similarly situate. 



Interesting electro-physiological researches have been made by Pro- 

 fessor Matteucci of Pisa, from which he has deduced the following 

 results. First. Muscle is a better conductor of electricity than nerve; 

 and nerve conducts better than brain. The conducting power of 

 muscle may be taken as four times greater than that of brain or nerve. 

 Secondly. In the muscles of living animals, as well as of those recently 

 killed, an electric current exists, which is directed from the interior of 

 each muscle to its surface. The duration of this muscular current 

 corresponds with that of contractility ; in cold-blooded animals, there- 

 fore, it is greatest : in mammalia and birds very brief. Temperature 

 has a considerable influence on the intensity of the current, a small 

 amount of electricity being developed in a cold medium ; a larger one 

 when the medium is moderately warm. Any circumstance that enfeebles 

 the frogs (the animals experimented on) and deranges their general 

 nutrition, diminishes the power of the muscles to generate electricity, 

 as it likewise impairs the contractile force. The muscular current 

 appears to be quite independent of the nervous system. It is unin- 

 fluenced by narcotic poisons in moderate doses, but is destroyed by 

 large doses, such as would kill the animal. The developement of this 

 muscular current seems evidently to depend on the chemical action 

 constantly taking place as an effect of the changes accompanying nutri- 

 tion. Thirdly. In frogs an electric current exists, which is distinct 

 from the muscular current. It proceeds from the feet to the head, 

 and is peculiar to batrachian reptiles. Fourthly. Singular results are 

 obtained by applying electricity in various ways to nerves. On making 

 experiments on the sciatic nerves of rabbits, he found that on closing 

 the circuit of the direct electric current, or the current passing from 

 the brain to the nerves, contractions in the muscles of the posterior 

 limbs were produced ; whilst opening this circuit was followed by marked 

 signs of pain, with contraction of the muscles of the back, and feeble 

 contractions of the posterior limbs. On closing the circuit of the inverse 

 current, or that directed from the nerves to the brain, signs of pain, 

 contractions of the muscles of the back, and feeble contractions of the 

 posterior limbs were produced. On opening it, contractions of the pos- 

 terior limbs followed. 1 



With regard to the hypotheses which ascribe muscular contractility 

 to the chemical composition of the fibre, and that which maintains, that 

 the property is dependent upon the mechanical structure of the fibre, 

 they are undeserving of citation, notwithstanding the respectability of 

 the individuals who have written and experimented on the subject. 

 They merely seem to show, that here, as in every case, a certain che- 

 mical and mechanical constitution is necessary, in order that the vital 

 operation, peculiar to the part, may be accomplished. 



But not only is it necessary, that the muscle shall possess a proper 



1 For an account of Matteucci's researches, see Todd and Bowman, Physiological Ana- 

 tomy and Physiology of Man, vol. i., Lond., 1845, and, especially, Matteucci, Lectures on the 

 Physical Phenomena of Living Beings, by Pereira, Amer. edit., pp. 176 and 224, Philad., 

 1848. 



