54 



ANIMAL MECHANISM. 



in a muscle when its nerve is divided. This paralysis takes 

 place also under the influence of curare^ although this poison 

 appears to act more slowly on the electric nerves than on the 

 greater part of the nerves of motion. Indeed, the electric 

 tetanus, to employ the happy expression of A. Moreau, is 

 manifested, not only when the nerve of the torpedo is sub- 

 jected to excitations very rapidly succeeding each other, but 

 also when the animal is poisoned with strychnine or any 

 other tetanizing substance. 



It was natural enough to compare the different cells or 

 laminae of the electrical apparatus in fishes, with the elements 

 of the voltaic pile, and following up this idea, to inquire what 

 was the electro-motive power of each of these little elements, 

 and what were the effects of tension resulting from the 

 association of these pairs. The following is the result of the 

 experiments of Matteucci. 



A portion of the electrical apparatus of the torpedo, placed 

 en ra'pport with the extremities of a galvanometer, gives 

 birth to a current of the same order as that in the apparatus 

 of which it formed a part. The longer the prism thus 

 detached, the more numerous must be the elements of this 

 kind of animal pile, and the greater the deflection of the gal- 

 vanometer at the moment of its discharge ; this is produced 

 by exciting the nervous fibre which corresponds with the 

 small portion of the electrical apparatus of the torpedo placed 

 on the pads of the galvanometer. Thus far, the analogy of 

 the electric apparatus with the pile is perfect, since the effects 

 of tension increase with the number of elements w^hich are 

 employed. This analogy holds good with all the electrical 

 fishes, when we endeavour to compare the intensity of the 

 currents obtained in different parts of the apparatus. 



In the torpedo it is found that the discharges are at their 

 maximum when we touch the two surfaces of its apparatus on 

 the inner side, that is to say, at the thickest part, which con- 

 tains the greatest number of discs superposed on each other. 

 In the gymnotus, whose electrical prisms have so great a 

 length, it is found that the discharge is stronger still, on 

 account of the greater volume and number of the elements. 

 It is proportional to the extent of space contained between the 



