NATURAL HISTORY. 



803 



membranous sides or sheaths of the 

 columns, which are presently io be 

 described ; and between these pro- 

 cesses the fascia covers the end of 

 each column, :i)aki!ig the outermost 

 or first partition. Each organ is 

 about live inches in length, and, at 

 the anterior end, three in breadth, 

 though it is little more tJian half as 

 broad at the posterior extremity : 

 each consists wholly of perpendicu- 

 lar columns, reaching from the up- 

 per to the under surface of the body, 

 and varying in their lengths accord- 

 ing to the thickness of the parts of 

 the body where they are placed, the 

 longest column being about an inch 



► and a half, and the shortest about 

 one fourth of an inch in length, and 

 their diameters about two tenths of 

 an inch. The figures of these co- 

 lumns are very irregular, varying 

 according to situation and other cir- 

 cumstances. The greatest number 

 are either irregular hexagons, or ir- 

 regular pentagons : but from the ir- 

 regularity of some of them, it hap- 

 pens that a pretty regular quadran- 

 gular column is sometimes farmed. 

 Those of the exterior row are either 

 quadrangular or hexagonal, having 

 one side external, two lateral, and 

 ^ either one or two internal. In the 



i second row they are mostly penta- 

 gons ; their coats are very thin, and 

 seem transparent, closely connected 

 with each other, having a kind of 

 loose net-work, of tendinous fibres, 

 passing transversely and obliquely 

 between the columns, and uniting 

 them more firmly together. These 

 arc mostly observable where the 

 large trunks of the nerves pass: the 

 columns are also attached by strong 

 inelastic fibres passing directly from 

 the one to the other. The number 

 of columns in dilferent forpedos, of 

 rather smalt size, appears to be a- 

 bout 470 in each organ, but the 



number varies according to the size 

 of the fish ; and in a very large tor- 

 pedo, the number of columns in one 

 electric organ was llS'i: they must, 

 therefore, increabe, not only in size, 

 but in number, during the growth of 

 the animal; new ories forming, per- 

 haps, every year on the exterior 

 edges, as they are much the smallest. 

 This process may be similar to the 

 formavion of new teeth in the human 

 jaw, as it increases. Each column 

 is divided by horizontal partitions, 

 placed over each other at very small 

 distances, and forming numerous in- 

 tei'stices, which appear to contain a 

 fluid. These partitions consist of a 

 very thin membrane, considerably 

 transparent ; their edges seem to be 

 attached to each other, and the 

 whole is attached by a fine cellular 

 membrane to the inside of the co- 

 lumns. They are not totally detach- 

 ed from each other, and I have found 

 them at different places adhering to 

 each other by blood-vessels passing 

 from one to another. 'I he number 

 of partitions contained in a column 

 of one inch in length, of a torpedo 

 which had been preserved in proof 

 spirit, appeared, upon a careful ex- 

 amination, to be 150 ; and this num- 

 ber, in a given length of column, 

 appears to be common to all sizes, 

 in the same state of humidity ; for 

 by drying they may be greatly al- 

 tered : whence it appears probable, 

 that the increase in the length of a 

 column, during the growth of the 

 animal, does not enlarge the distance 

 between each partition in propor- 

 tion to the growth, but that new 

 parfitionfc are formed, and added to 

 the extremity of the column, from 

 the fascia. The partitions arc very 

 vascular ; the arteries are branches 

 from the veins of the gills, which 

 convey the blood that has received 

 the inlluence of respiration. They 

 3 F 2 pass 



