FISH IN GENERAL. 53 



readily convertible into soap, and then produces oleic acid, 

 glycerine, and a minute portion of margaric acid. 



The skeleton of osseous fishes in general is composed of the 

 head ; of the respiratory apparatus, having always a consider- 

 able bony development ; of the trunk embracing both body 

 and tail; and of the members which are the pectoral and 

 ventral fins ; the vertical fins, or those of the back, anus, and 

 tail, may be regarded as belonging to the trunk. In the head 

 may be distinguished the cranium, the maxillae, the bones 

 beneath the cranium, and behind the maxillae, serving to 

 suspend and move them ; the bones of the opercula, those 

 surrounding the nostril, the eye, and temples, or those which 

 cover a part of the cheeks. The respiratory apparatus con- 

 tains the os hyoides and its appendices, that is, the branchios- 

 tegous rays, and the arches which support the branchiae, and 

 the different pieces and arches which are connected with them, 

 and perform the offices of larynx and trachea ; and finally, 

 the bones at the entrance of the pharynx, forming a kind of 

 secondary jaws. 



The trunk is composed of the vertebrae of the back and tail 

 (for there is no real neck nor sacrum) of the ribs, of the inter- 

 spinal bones which form the root of the dorsal and anal fins, 

 and of the rays of those fins, including also the caudal. 

 These rays, whether they be branched and articulated, or 

 simply spinous, may be always divided lengthways into 

 halves. Fish seldom have a true sternum, and where it 

 exists, pieces almost external compose it, and unite the infe- 

 rior extremities of the ribs. 



The anterior extremity or pectoral fin contains the shoulder, 

 the bony semi-circle composed of several pieces, and sus- 

 pended above from the cranium on the spine, and below, 

 united to the corresponding bone of the other side. Two 

 bones comparable to the cubitus and radius bear upon their 

 edge a row of little bones, apparently the representatives of 



