OR LIGAMENTS. 125 



and ligaments become more developed and distinct. The 

 vertebral ligaments of osseous fishes are white, fibrous, and 

 dense in their texture, and by their elasticity they bring 

 back forcibly the vertebral column to the straight position 

 when it has been drawn to either side by the lateral strata 

 of muscles. The moveable intermaxillary, palatine, and 

 superior jaw bones are connected by a tough fibro-cartilagi- 

 nous membrane, as well as by muscular attachments. The 

 moveable articulations of fishes are mostly effected by a 

 tough interposed cartilage, which envelopes the contiguous 

 ends of the bones. This substance is much softer than the 

 corresponding fibro-cartilaginous parts of higher classes, and 

 is more readily dissolved by boiling water. In place of the 

 interposed elastic sacs between the cup-like cavities of the 

 vertebrae of fishes, or the firm connecting layer of fibro- 

 cartilage between the vertebrae of mammalia, we find the 

 bodies of the vertebrae of reptiles united by distinct move- 

 able articulations, or enarthroses, with strong capsular liga- 

 ments and synovial secretion, and many of the vertebrae of 

 birds, especially of the neck, are united by the same free 

 and secure articulations. In the amphibia and in the rep- 

 tiles, most of the articulations are constructed on a simpler 

 plan than in the warm-blooded classes ; there is yet no in- 

 ter-articular cartilage between the condyle of the lower jaw 

 and the temporal bone, nor a ligarnentum teres between the 

 femur and the cotyloid cavity ; but the articular surfaces 

 of the long bones are covered with smooth and firm carti- 

 lage, are lubricated with synovia, and are enclosed in strong 

 capsular ligaments. The articular processes of the vertebrae 

 have here their synovial capsules, and the spinous processes 

 their inter-spinal ligaments. The articular cavities of the 

 joints are less deepened by cartilaginous margins, the inter- 

 nal loose cartilages of the joints are more rare, the exterior 

 ligamentous bands are more simple in their arrangements, 

 and there are fewer immoveable synarthroses than in birds 

 and mammalia. The capsular ligaments are thinner, and of 

 a more dense texture in birds than even in mammalia, and 

 more synovia is poured into the joints, especially of the 

 neck and extremities, on account of the extent and rapidity 

 of their movements and the high temperature of their body. 

 Each end of the tympanic bone is here enveloped in its 



