258 SKELETON OF THE BABBIT 



however, in the adult so intimately associated with the bones 

 of the jaws that they may conveniently be described with the 

 skeleton. The hairs and claws, which are special develop- 

 ments of the epidermis, or surface-layer of the skin, will be 

 described in the following chapter. 



The rabbit's skeleton may be divided, like that of the dog- 

 fish, into axial and appendicular portions, which will be dealt 

 with successively. 



The following points in the rabbit's skeleton should be 

 noticed as characteristic of the great majority of mammals, 

 and as separating them from lower vertebrates. 



The vertebral centra bear epiphyses at their ends, and the 

 successive vertebrae are connected by inter-vertebral ligaments : 

 the cervical vertebrsB are seven in number. The sternum is 

 transversely jointed. In the skull, there is a completely ossi- 

 fied occipital ring, with two condyles : the cranial and olfactory 

 cavities are separated by a bony cribriform plate : there is not 

 a distinct para-sphenoid on the imder surface of the skuU : the 

 lower jaw articulates directly with the squamosal : there are 

 three or four small but distinct auditory ossicles, of which the 

 incus probably represents the quadrate of lower vertebrates : 

 the teeth form a single row round the margin of each jaw, and 

 are arranged in groups. In the shoulder girdle, the coracoid 

 is reduced to a smaU process of the scapula ; and there is no 

 inter-clavicle. The ankle-joint is situated between the tibia 

 and fibula, and the proximal tarsal bones : the fourth and 

 fifth carpalia, and the corresponding tarsaHa, fuse to form a 

 single bone in each limb : the preaxial digits, corresponding 

 to the thumb and great toe, have two phalanges, while the 

 others have each three. 



Excvmine the prepared skeletons, and make drawings to 

 scale of the several parts. 



Skeletons may be prepared by macerating in water for 

 some weeks. The skull may with advantage be longitudinally 

 bisected. In the dried skeletons the cartilaginous portions are 

 lost. 



