52 SUPPLEMENT ON 



great variety of motions. Thus by means of a ginglymus, the 

 under jaw and operculum are attached to the pteropalatine 

 apparatus, and that apparatus to the cranium. There are 

 others in the articulation of the rays of the dorsal and anal 

 fins with the interosseous bones, and in that of the first ray of 

 the pectorals with the bone corresponding to the radius. 

 They have even two kinds of determinate movements by 

 articulation, which do not occur in other classes of animals ; 

 that, obtained by means of two links or annulations joined 

 together as it were of a chain, and that which at the will of 

 the fish is either very moveable or quite fixed. Both occur 

 in the structure of siluri. The articulations for determined 

 movements offer ligaments, cartilage on the surface of the 

 bone, and a synovial liquor as in animals of the superior 

 classes. The articulation of the joints of the vertebrae is 

 effected by means of a fibro-cartilaginous substance, which 

 passes through them, and which, in some cases, as in stur- 

 geon and lamprey, assumes the form of a cord ; and it is also 

 by similar fibro-cartilaginous substances that the several 

 pieces of the opercula, of the branchial apparatus, of the 

 humeral, brachial, and carpal bones, and of the pelvis, are 

 connected, and that the last-mentioned are fastened to those 

 of the shoulder. 



The chemical composition of these bones presents an 

 organic base penetrated by earthy matter. The earthy matter 

 consists of phosphate of lime and of magnesia with oxide of 

 iron, which maybe supposed to be united to phosphoric acid ; 

 there is also some sub-carbonate of lime. As for the animal 

 matter, the part azotized constitutes the base of cartilage ; the 

 rest fatty, forming an oil that pervades it. The cartilage of the 

 bones of fish differs from that of mammiferce and birds, since 

 it does not afford gelatine when boiled. The oil is principally 

 composed of oleine, slightly impregnated with an odorous 

 principle, and a yellowish colouring substance. This oil is 



