But the mechanical arrangement and physiology of the lateral muscles of the body of fishes constitute my present object. These parts have already been described in a general way by Professor Camper, M. Vicq-d-Azyr, and M. Cuvier, to whom I am indebted for much useful information. They have been denominated "couches musculaires" by M. Vicg-d-Azyr,[1] and "muscles laterals" by M. Cuvier.[2] The term used by M. Cuvier seems very appropriate for the general division or class. But, as the flakes are arranged in distinct longitudinal rows, these rows must be considered as orders. And, as "couches" appears objectionable, I shall adopt series in its stead; distinguishing each by a word referring to its situation in the animal, viz, the dorsal, vertebral, abdominal, and ventral series.
These series are composed of thin masses of muscle, or, as they are commonly called, flakes; which for the most part are thicker upon their outward edges, and become wedge-shaped towards their interior attachments. Each series is separated from the next adjoining by a membraneous partition, which is most apparent between the vertebral and abdominal series.
The dorsal series () arises from the back of the head. In its course it is terminated on the upper edge by the bones, which support the single fins, and a membranous septum: at this part the flakes are thin. Its lower margin is bounded by the vertebral series, where the flakes become gradually thicker. The first flake is composed of longer fibres than the rest, and possesses more red blood. Those succeeding it
