480 - PHILOSOPHICAL TKANSACTIONS. [aNNO 1773. 



transversely and obliquely, between the columns, and uniting them Inore firmly 

 together. These are 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 different torpedos, of the size of that now offered 

 to the society, appeared to be about 470 in each organ ; but the number varies 

 according to the size of the fish.* These cohuTins increase, not only in size^ 

 but in number, during the growth of the animal : new ones forming perhaps 

 every year on the exterior edges, as there they are much the smallest. This 

 process niay be similar to the formation 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 interstices, which appear 

 to contain a fluid. These partitions consist of a very thin membrane, con- 

 siderably transparent. Their edges appear to be attached to one another, and 

 the whole is attached by a fine cellular membrane to the inside of the columns.) 

 I'hey are not totally detached from one another : I have found them adhering, 

 at different places, by blood vessels passing from one to another. 



The number of partitions contained in a column of 1 inch in length, of a 

 torpedo which had been preserved in proof spirit, appeared on a careful examina- 

 tion to be 150: and this number in a given length of colunui, appears to be 

 common to all sizes in the same state of humidity ; for by drying them they 

 may be greatly altered : 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 proportion to that growth ; but that new 

 partitions are formed, and added to the extremity of the column from the fascia. 

 The partitions are very vascular ; the arteries are branches from the veins of 

 the gills, which convey the blood that has received the influence of respira- 

 tion. They pass along with the nerves to the electric organ, and enter with 

 them ; they then ramify, in every direction, into innumerable small branches on 

 the sides of the columns, sending in from the circumference all around, on each 

 partition, small arteries, which ramify and anastomose on it ; and passing also 

 from one partition to another, anastomose with the vessels of the adjacent parti- 

 tions. The veins of the electric organ pass out, close to the nerves, and run 

 between the gills, to the auricle of the heart. 



The nerves inserted into each electric organ, arise by 3 very large trunks, 

 from the lateral and posterior part of the brain. The first of these, in its passage 

 outwards, turns round a cartilage of the cranium, and sends a few branches to 

 the first gill, and to the anterior part of the head, and then passes into the 

 organ towards its anterior extiemity. The 2d trunk enters the gills between the 



* In a very large torpedo, the number of columns La one electric organ were 1182.^0rig. 



