Observations on certain parts of the animal oeconomy. Inclusive of several papers from the Philosophical transactions, etc / by John Hunter ... With notes by Richard Owen.
- John Hunter
- Date:
- 1840
Licence: Public Domain Mark
Credit: Observations on certain parts of the animal oeconomy. Inclusive of several papers from the Philosophical transactions, etc / by John Hunter ... With notes by Richard Owen. Source: Wellcome Collection.
415/494 page 407
![a fine cellular membrane to the inside of the columns. They 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 one inch in length, of a torpedo which had been preserved in proof spirit, ap- peared on a careful examination to be one hundred and fifty; and this number 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 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 that - extremity of the column from the fascia. The partitions are very vascular;* the arteries are branches from the vessels of the gills which convey the blood that has re- ceived the influence of respiration. They pass along with the nerves to the electric organ, and enter with them; then they ramify in every direction into innumerable small branches upon the sides of the columns, sending in from the circumference all around upon each partition small arteries, which ramify and anastomose upon it, and passing also from one partition to another, anastomose with the vessels of the adjacent partitions. | 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 three 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 ante- rior part of the head, and then passes into the organ towards its anterior extremity.t The second trunk enters the giils between the first and second openings, and after furnishing it with small branches passes into the organ near its middle. The third trunk, after leaving the skull, divides itself into two branches, which pass to the electric organ through the gills; one between the second and * [See prep. 2176, which is the section of a Torpedo, of very large size, taken in Torbay in August, 1774. It weighed fifty-three pounds, was four feet in length, two feet and a half in breadth, and four inches and a half in thickness, Mr. Hunter having received this fish in a recent state was enabled to inject it, and thus demonstrate the vascularity of the electrical organs. ] + [This nerve is a part of the third division of the fifth pair, and does not greatly exceed the size of the corresponding nerve in other species of the ray tribe; it distributes branches to the mucous tubes, which are fewer in number in the torpedo than in the ordinary rays, before it penetrates the electric organ. The other great fasciculi of nerves correspond with the pneumogastric, or eighth pair of nerves: a large branch is continued from the most posterior to the stomach, where it is spread over the great arch. Dr. John Davy conjectures that the superfluous electricity when not required for the defence of the animal may be directed to this organ to promote digestion. In the instance of a Torpedo which he preserved alive for many days, and which was frequently excited to give shocks, digestion appeared to have been completely arrested ; when it died, a small fish was found in its stomach, much in the same state in which it was swallowed ; no portion of it had been dissolved.]](https://iiif.wellcomecollection.org/image/b33292292_0415.jp2/full/800%2C/0/default.jpg)
