NATURAL PHILOSOPHY. 115 



trol of the remainder of a current, that cannot be overcome. When 

 this moment has come, he strains all the muscles of one arm, so as to 

 establish an equilibrium between the flexors and extensors of all the 

 joints of the arm. At once the needle moves, and the direction of the 

 movement is such as to indicate in the stiffened arm, an inverse cur- 

 rent, according to the notation of Nobili ; that is, a current directed 

 from the hand to the shoulder. When the experiment is made with 

 the galvanometer by M. Reymond himself, the deflection amounts to 

 30. He obtains, however, movements in the needle of far greater 

 extent by contracting alternately the muscles, first of one arm and 

 then of the other, in time with the oscillations of the needle. On 

 bracing simultaneously the muscles of both arms, very small devi- 

 ations are observable, sometimes in one direction, and sometimes in 

 another ; and these minute deflections are evidently caused by the 

 difference between the contractile force of the two limbs. Hence it 

 arises, that when the experiment is repeated many times successively, 

 the results diminish gradually in amount. The amount of deviation 

 depends upon the amount of the development and the exercise of the 

 muscles. The habitual superiority of the right hand over the left, in 

 this experiment, is to be interpreted by the preponderance of the 

 amount of deflection produced by the tension of the ri^ht arm. M. 



j 



de Humboldt says, " The fact of the experiment affecting a mag- 

 netic needle by the alternate tension of the muscles of the two arms, 

 an effect due to volition, is established beyond the shadow of a 

 doubt. Notwithstanding my advanced years and the little strength 

 that I have in my arms, the deflections of* the needle were very con- 

 siderable." To facilitate the experiment, it is advisable to plunge the 

 forefingers into the water, and to support the palms of the hands, 

 to enable one to brace up well the muscles of the arm, which it is 

 purposed to bring into play. 



Since the announcement of these experiments, many persons have 

 tried similar ones, and only in a single case that of M. Becquerel 

 have we seen any failure noticed. 



ANIMAL ELECTRICITY. 



MR. ALFRED SMEE, an English surgeon, and the inventor of the 

 battery which bears his name, announces some important discoveries 

 in animal electricity. By a test which he calls electro-voltaic, he has 

 discovered that the terminations of the sensor nerves are positive poles 

 of a voltaic circuit, while the muscular substance is the negative 

 pole. The sensor nerves are the telegraphs which carry the sensa- 

 tion to the brain, and the motor nerves cany back the volition to 

 the muscles. The brain he infers to consist of five distinct voltaic 

 circles, which, upon theoretical grounds, he believes to be sufficient 

 to account for all the mental phenomena. He has succeeded in mak- 

 ing artificial electric fish, and artificial muscular substance. Should 

 these researches be fully confirmed by other investigators, they must 

 be regarded as affording the most important physiological discovery of 

 the age. 



