SKELETON OF THE EABBIT 265 



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 next 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. 



Epiphyses are present at the ends of the vertebral centra, 

 as well as at the ends of the long bones of the limbs ; and the 

 successive vertebrae are connected by inter- vertebral Ugaments : 

 the cervical vertebrae 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 under surface of the skull : 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 small process of the scapula ;. and there is no 

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

 and fibula above, and the proximal tarsal bones below : the 

 fourth and fifth carpalia, and the corresponding tarsalia, fuse 

 to form a single bone in each hmb : the preaxial digit, cor- 

 responding to the thumb, has two phalanges, while the others 

 have each three. In the rabbit the first digit of the hind limb, 

 corresponding to the great toe in man, is rudimentary: in 

 other mammals it bas two phalanges like the thumb. 



Examine the ^prepared skeletons and make drawings to 

 £cale of the several parts. 



