ELECTRO-PHYSIOLOGY. 337 



treraity of the fit^li to the other. The number of prisms in each of the organs 

 of the gymuotns is much less than in the torpedo, but in each of these prisma 

 are coutaiued about four thousand cellules or elementary organs. From these 

 numbers it results that the cellules of the organ of the torpedo are smaller than 

 those of the gymnotus, and accordingly ten diaphragms of a prism of the gym- 

 notus form a height wRich is six times greater than that occupied by ten dia- 

 phragms in the prism of the torpedo. The surface of the cellules is also very 

 different in the two organs : the cellule of the gymnotus has about fifty square mil- 

 limetres of surface, and that of the torpedo has only from six to eight millimetres. 

 In fine, the sum total of prisms in the organ of the torpedo is about ten times 

 greater than that of the prisms in the gymnotus. It may be appi'oximately as- 

 sumed that orfe of the two organs of the torpedo contains nine hundred and forty 

 thousand cellules, while the organ of the gymnotusf though larger, contains only 

 one hundred and ninety-two thousand cellules ; hence the volume of one of the 

 cells of the gymnotus is seventy or eighty times greater than the volume of the 

 cellule of the torpedo. The nerves distributed in the organ are ramified upon the 

 diaphragms which constitute the cellules, and are therefore extended in planes 

 transverse to the axes of the prisms. 



Very recently Pacini and some of the anatomists of Germany have assured 

 us that in every diaphragm there are found two laminae, one of connective cel- 

 lular tissue, and the other, which they have termed the electrical lamina, of 

 nervous elements. There would seem to exist a relation between the position 

 of this electrical lamina and the relative distribution of the poles in different 

 electrical fishes. If this relation were well demonstrated and generalized it would 

 furnish an important datum for the theory of the electric organ. 



After these anatomical statements we will proceed to a consideration of the 

 fundamental fact on Avhich rests the theory of these electro-motors, and which 

 leads to the conclusion that the cellule of the organ is the elementary electro- 

 motor of that organ. To show this, I detach from the organ of the living tor- 

 pedo a portion as small as possible, and remembering the position which this 

 portion occupied with reference to the faces of the fish, I apply the extremities 

 of the galvanometer to the bases of the prisms of the portion in question. If 

 I now irritate, in any manner, the nervous filaments of this detached piece, I am 

 secure of obtaining the discharge, and consequently the deviation of the needle 

 in the same direction it would have with the entire organ. This experiment may 

 be made on a piece of the organ not larger than the head of a pin ; for if we 

 place upon this the nerve of a galvanoscopic frog and wound the piece with a 

 very fine forfex, we at once observe the contraction of the frog. 



Among the stimulants applied to the nerves of the organs, the electric current 

 was naturally considered. For this purpose one of the organs of a living tor- 

 pedo is rapidly detached, and by an incision the nerves distributed within it are 

 exposed to view. It is best to keep each of these nerves suspended by a silk 

 thread, and galvanoscopic frogs are distributed on the sorface of the organ to 

 indicate the discharges. An electric current is then made to pass now into one 

 and now into another of these nerves. The discharge obtained is constantly in 

 the usual direction in the galvanometer — that is, from the back to the belly. On 

 separately irritating different nerves, the contractions of the frogs show that the 

 discharge occurs each time in the portion of the organ in which the irritated 

 nerve ramifies. Under the irritation produced by the current on the nerves the 

 discharge of the electric organ pursues a like course with the muscular con- 

 traction. At first, when the organ is scarcely fatigued, there is a discharge as 

 well at the opening as at the closing of the circuit; when the excitability of the 

 nerves is enfeebled the discharge occurs at the commencement of the direct and 

 the end of the inverse current. 



I have sought to discover whether the function of the electric organ is ac- 

 companied by a variation of the volume or of the form of the organ. For this 

 22 s 



