Page:Philosophical Transactions - Volume 096.djvu/18

8 with those of the vertebral series, the apex of which is presented towards the head. They are attached internally to the transverse and inferior spinous processes of the vertebrae. The ribs are placed in the line of the centre partition, and lie between the flakes. This series arises from a bone which borders the opening for the gills, and the pectoral fin, with its scapula and muscles, is situated between its foremost flakes. Wherever this series encloses the viscera, its flakes are shallow, and their thickness internally is not much less than at their external superficies.

Lastly, the flakes of the ventral series (ii) form acute angles with the abdominal flakes, the points of which incline to the tail. It is attached anteriorly to the os hyoides, and the bones of the lower jaw. In its course it is bounded above by the abdominal series, and below by a membranous septum, within which the inferior single fins arise. The flakes, that cover the viscera, are shallow; and they lie more oblique as they approach the tail. Both this, and the last described series, have their muscular fibres arranged according to the length and figure of the fish.

Three large superficial nerves (kk) passing longitudinally from the head to the tail, in the course of the membranous partitions, give off fibrils at right angles, which bend inwards between each of the muscular flakes. A larger set of nerves are sent from the medulla spinalis, one between each flake, the branches of which seem to enter without ramifying there. Another small nerve passing from the head, and running deep-seated, and close to the dorsal spines, crosses and unites with each of the spinal fibrils, and at the junction a remarkable body appears; it is a loose transparent vesicle, about the