SCIENCE. 



29 



course to a third science, experimental physiology, to 

 unite anatomy with natural philosophy, and thus make 

 the result of one answer for the other. Whoever wishes 

 to acquire a clear idea of the three electric fish and their 

 organs must moreover keep the following points always 

 uppermost in his mind : 



The electric fish already mentioned as representing 

 three different species are by no means individual fish 

 as may, perhaps, be supposed. On the contrary, they 

 are in form very similar to those belonging to the same 

 families. For instance, the electric eel resembles, to an 

 extreme degree, the common eel, the electric silurus 

 those of its species inhabiting our rivers and lakes, and 

 the torpedo all others of the ray family. Ancient 

 zoology associated the electric fish with others of its kind 

 which possessed no electric capacity whatever. 



In each of these fish the electric organ is constructed 

 in a unique and highly interesting manner. The most 

 simple of all is that of the torpedo. This creature pos- 

 sesses two electric organs, symmetrically placed, one on 

 each side. Like all fish of the ray species it is distin- 

 guished by a flat, broad body. However, while the ray 

 usually has a somewhat pointed head, the torpedo has a 

 remarkably wide one. This arises from the fact that in 

 addition to the gills on each side of the head, the falci- 

 form electric organs discovered by Redi are also situated 

 there. They extend along the body, one directly under 

 the skin of the back, the other beneath the skin of the sto- 

 mach. The dimensions of these organs is especially 

 worthy of attention. In a torpedo of ordinary size (35 

 centimetres in length) the electric organ is about 1 1 cen- 

 timetres long, the greatest width 5 centimetres, and the 

 height, (the skin being removed from the back and sto- 

 mach), 2 centimetres. When prepared, the organ is of 

 the consistency and not unlike a gray, semi-transparent 

 gelatinous substance. 



In the electric silurus, as in the torpedo, a symmetri- 

 cally placed organ is found on each side. It lies on the 

 skin which assumes the thickness of a tough rind. With 

 the exception of the extremities, (the tip of the head and 

 tail), the substance of these organs is embedded in the 

 entire skin of the fish. In the middle line of the back and 

 stomach the two organs come in direct contact, so that 

 we may say the body of the silurus is placed in a tube 

 composed of the two electric organs which unite like two 

 gutter tiles. From the ends of this tube the head and 

 tail of the fish alone project, as the skin covering them 

 contains no electric substance. When in a fresh condi- 

 tion the material composing the organs presents very 

 much the same appearance as that of the torpedo. The 

 size is considerable, the weight being more than one- 

 fourth that of the entire body. 



The electric organs of the gymnotus are by far the 

 most extensive. This creature, the largest specimen of 

 whose species measures the length of a man and the 

 thickness of a good-sized thigh, does not possess the 

 same strongly-developed, muscular constitution which 

 distinguishes our common eel. Almost the whole body 

 from the back of the head to the end of the tail is com- 

 posed of electric organs which are situated along the ver- 

 tebral column in two pairs, a large one above and a small 

 one beneath. Above these organs, and aside from the 

 vertebral column, are the muscles (reduced to very in- 

 significant dimensions) which move the powerful body. 



This, then, is the way in which the electric organs are 

 distributed among the three fish, without causing them 

 to differ in any other respect from the remainder of their 

 species. Yet we must make one limited addition to this 

 assertion. 



The electric organs are all distinguished by an extra- 

 ordinary abundance of nerves. To each individual organ 

 is attached an immense number of nerve-fibres, which 

 complete it in some remarkable way yet to be spoken of, 

 and which must be regarded as a constituent part of the 

 organ itself. 



It is, of course, understood that these nerve-fibres 

 (called electric nerves) are entirely wanting in the organi- 

 zation of the non-electric fish, and nothing analagous with 

 them can be found in the latter's entire construction. 



But we must go a step further. It is a fixed law, gov- 

 erning the entire vertebrate world, that every nerve shall 

 spring from a particular point, or rather from a certain 

 group of cells belonging to the organs of the nerve 

 centres (brain. and spinal cord). This group is called the 

 centre of origin of these nerves. In many cases the in- 

 dividual nerve-fibres have been successfully traced to the 

 separate ganglion groups (nerve cell groups) of a like 

 number of cells. In these cells single apophyses have 

 been well authenticated and make it evident that the lat- 

 ter become nerve-fibres in course of time ; or rather the 

 nerve fibres have been carefully observed as to their po- 

 sition in regard to the centre of origin, and thus warrant 

 the conclusion that they unite with the apophyses of the 

 ganglion cells. 



In the torpedo the powerful electric nerves (five on 

 each side) unite with the centre organ between the bram 

 and spinal column, and form their centre of origin on 

 each side in a massive lobe first described by Alexander 

 von Humboldt, and called the lemon lobe on account of 

 its peculiar color. Now the name has been changed to 

 electric lobe. 



A close microscopic examination has shown that this 

 consists entirely of ganglion cells and nerve fibres. These 

 excited special interest for some time among anatomists, 

 as it was discovered that their dimensions much sur- 

 passed those of all other nerve fibres and ganglion cells. 



Then Bilhary disclosed the fact that in the electric sil- 

 urus, the numberless nerves which support the electric 

 organ originate from the subdivision of a single collossal 

 nerve ; also that this enormous fibre springs from an 

 equally large ganglion cell visible to the naked eye, which 

 lies imbedded in a substance of its own not far from the 

 upper end of the spinal column, and forms the electric 

 centre of origin of the fish. 



The nerves which constitute the electric organ of the 

 gymnotus are unusually great in number (200 — 230 on 

 each side). They are situated along the entire length of 

 the spinal column and at each interval between two dorsal 

 vertebra a nerve projects. Their origin has not yet been 

 explained in a satisfactory manner, but the most probable 

 supposition is that they spring from certain large ganglion 

 cells which are found along the spinal column. 



The above details show us that the three electric fish 

 possess specific electric organs and electric nerves, and 

 that the construction and situation of the central organs 

 differs exceedingly from that of the nerves. If a closer 

 examination is made, it will be seen that the three electric 

 organs harmonize perfectly with the essential parts of 

 their structure, and that an anatomical principle binds 

 them together. 



This anatomical principle is nothing more than the con- 

 struction of the electric organs out of many thousands of 

 perfect, symmetrically arranged layers, the so-called elec- 

 tric strata in which the nerves terminate. Apart from 

 these layers there is no other demonstrable formula of the 

 electric organs except blood vessels and tissues. 



In the electric organ of the torpedo which lies between 

 the paralleled flat portions of the back and stomach, the 

 electric layers are arranged in a corresponding manner. 

 They are distinguished by having a rough and a smooth 

 side. The latter is turned towards the back, the former 

 towards the stomach. The rough side is so called from 

 the countless nerve ramifications which spread themselves 

 on all sides, and at last become so diminutive that they 

 appear to melt into the electric layers composed of a 

 pithy, albumen-like substance. It is very much to the 

 point that these thousands of layers should be identified 

 as a summary of electro-motory units, and that the con- 

 struction of each individual layer should be investigated 

 in order to discover, if possible, the reason for the phen-> 



