SCIENCE. 



omenon. The fact that the nerves of the layers turn to- 

 wards the negative flat portions of the fish when the -shock 

 takes place, appeared to give a by no means unimportant 

 hint, and to indicate a relation existing between the dispo- 

 sition of the nerves and that of the shock. 



With the gymnotus all the different proportions har- 

 monize completely with each other. The electric layers 

 are situated vertically along the body. A rough and a 

 smooth side are quite distinct. In the latter numberless 

 nerves are embedded. The rough side corresponds to the 

 tail and the smooth side to the head. The same relations 

 exist here as in the torpedo. With the gymnotus, how- 

 ever, the current goes from head to tail, and when the 

 electric shock takes place, the nerves of the strata turn 

 towards the negative pole of the fish. 



This harmony between the nerves and the electric 

 shock leads us to suppose that an effectual and universally 

 recognized law is in question. Yet, while the whole 

 world was expecting a like agreement in regard to the 

 malopternus, anatomical and physical investigations of its 

 organs showed a considerable difference existing between 

 them and the two first described. It is true that electric 

 layers are there, and also situated vertically along the 

 creature's body. The nerves too, unite in the same man- 

 ner and on the same side with the layers. But a rough 

 and a smooth side cannot be distinguished here as in the 

 torpedo and gymnotus, for the layers are not furnished 

 with so great a number of nerve fibres. On the contrary, 

 one single nerve fibre is implanted in the centre and cor- 

 responds with the tail of the fish, as is the case of the 

 gymnotus. When the shock takes place, however, this is 

 the positive and not the negative pole. 



So far, no one has succeeded in removing this contra- 

 diction, and it is more than questionable whether the re- 

 semblance agreed upon by Pacini between the anatomical 

 and physical relations of the electric layers, has really the 

 value of a natural law or not. In laying down this prin- 

 ciple an important anatomical fact is first to be considered 

 which later years have succeeded in ascertaining. It has 

 been said that the electric layers in the gymnotus possess 

 an identical microscopical structure, which formerly 

 was only known in the torpedo and silurus. Un- 

 fortunately, the gymnotus has not been successfully exam- 

 ined in regard to this, therefore the question concerning 

 the physical explanation of the electric shock has not 

 much significance. 



These are the facts which Anatomy is capable of pro- 

 ducing in regard to the structure of the electric organs, 

 especially in all that concerns their relations with the ner- 

 vous system. No less great is the number of facts ascer- 

 tained by the means of experimental physiology, which 

 first facilitated a thorough understanding of the electric 

 organs and their import. 



Before these facts are individualized, however, it is nec- 

 essary to make a few general remarks concerning the 

 physiology of the nervous system. 



All the organs contained in the body with which those 

 springing from the centre of origin of the nervous sys- 

 tem unite, can be divided into two classes, according to 

 the relation they bear to the nervous system. 



First class : Organs with centripetal nerves (commonly 

 called organs of sense). These are characterized by the 

 fact that any influence directed upon them through the 

 nerves is conducted to the organs of the nervous system, 

 and there produces a sensation. This perception arises 

 from the peculiar nature of the nerve in question. If the 

 retina of the eye is attracted by anything, a sensation of 

 light is produced, which influences the nerves of the skin. 

 Any excitation of the organs of hearing causes a resound- 

 ing sensation upon the nerves. Indeed, it is not even 

 necessary that the corresponding organ should be directly 

 attached at all. The same effect is produced when the 

 nerve of the organ is cut and any excitation made upon the 

 end which does not unite with the central organ. If the 

 influence is directed upon the periphery end of the divided 



nerve which is attached to the organ of sense, no natural 



effect will be perceived. 



Second class : Terminal organs with centrifugal nerves. 

 These do not include the organs of sense, according to any 

 general signification. The muscles, the organs of sight, 

 and probably the glands, all belong here. These organs, 

 differing so completely one from the other, bear the same 

 general relations towards the nervous system. Every in- 

 fluence which effects the centre of origin, particularly one 

 made at will by the animal in question, is conducted 

 through the nerves of the final organ, and, according to 

 the nature of the latter, produces muscular contraction. 

 Here also it is unnecessary that the excitation should pro- 

 ceed directly from the centre of origin. The same effects 

 appear when the nerve of the terminal organ is cut and 

 any influence directed upon it. If the excitation be directed 

 upon the end of the nerve in connection with the centre of 

 origin, there is no result. 



It is to the second class that the electric organs belong. 

 They are under the direct influence of the nervous system 

 just as other organs are. They are distinguished merely 

 by their peculiar properties, and they develop under the 

 controlling power of the nervous system just as the mus- 

 cles contract and expand by the same means. 



The proof of this analogy has been given in a most 

 complete manner by Physiology, and we will repeat it 

 here, or, rather, give the principal details. 



If the centre of origin of a muscle or any group of mus- 

 cles is excited in an animal, contraction takes place. A 

 needle thrust into the electric strata of a living torpedo 

 occasions an immediate electric discharge. 



The same results are observed when the excitation is 

 made upon the end of the nerve connected with a muscle 

 instead of the centre of origin. 



If an electric excitation is selected for this experiment it 

 will be seen that every irritation, however superficial, made 

 upon the nerve proceeding from the muscle is followed by 

 an electric shock. 



If the irritations follow each other in quick succession 

 the convulsions will be reduced to an apparently invaria- 

 ble state of contraction which Physiology designates as 

 tetanus. The same excitations directed upon the electric 

 organ produce the same effects. This is called electric 

 tetanus. 



It has been observed that a short space of time diii") 

 elapses between the nerve excitation and the beginning of 

 the convulsion during which the muscle remains perfectly 

 motionless. When the nerve of the electric organ is irri- 

 tated the same result occurs. 



The muscles and electric organs of animals which have 

 been poisoned by strychnine produce very interesting ef- 

 fects. The nature of this poison consists (as physiology 

 expresses it), in a condition of complete reflex irritability, 

 that is, a state in which every excitation experienced by 

 the nerves of sense is answered by some modification of 

 the centrifugal nerves. If, for instance, we take a rabbit 

 or frog which is poisoned by strychnine and shake it vio- 

 lently or scream loudly, you will see that spasmodic mus- 

 cular contraction follows each successive irritation. If an 

 electric fish is poisoned by strychnine the same contrac- 

 tions are produced, followed by an electric discharge. 



We must not forget to mention that the electric organs 

 as well as the muscles are liable to fatigue, and that just 

 as the latter lose their capacity for contraction after con- 

 tinuous labor, so are the former incapable of producing 

 any effect after repeated discharges have taken place. 



The immense number of concordant facts which can be 

 proved in regard to the electric organs and muscles, has 

 induced physiologists to assume that an especial anatom- 

 ical and physiological relation exists between them, and 

 many consider the electric organs to be muscles re- 

 modelled in some peculiar way in which the development 

 of electricity instead of force, and the electric shock 

 instead of contraction, had taken place by some inexpli- 

 cable means. Such suppositions as these stand in direct 



