^OQ STRUCTURE OF FISHES. 



Particular dc- the flakes contract partially, to give it a serpentine mo- 



scription of ^Jq^. To produce these eflfccts all the other scries co- 



the muscles of 



fishes. operate. 



The superior external edges of the flakes of the verte- 

 bral series (gg) form acate angles with the inferior exter- 

 nal edges of those of the dorsal series, the apices of which 

 point toward the tail : the flakes are larger, but their num- 

 ber is the same. The lower margin of this series is bounded 

 by the central membranous partition, which has already 

 been noticed to be more conspicuous than the other lon- 

 gitudinal diyisions, and It apparently admits of greater 

 motion. 



The abdominal series (hh) is composed of flakes similar 

 to the preceding. They range toward the tail, forming 

 an angle with those of the vertebral series, the apex o£' 

 which is presented toward 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 

 iBxternal superficies. 



Lastly, the flakes of the ventral series (?V) 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 fteptum, 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 muscu- 

 lar Xibres arranged according to the length and figure of 

 the fish. 



Three large superficial nerves {kk) passing longitudi-, 

 nally from the head to the tail, in the course of the mem- 

 branous partitions, give off" fibrils at right angles, which 

 bend inwards between each of the muscular flakes. A 

 larger set of nerves are sentfrom the medulla spinalis^ one 



bctwecBi 



