292 THE SKELETON OF THE RABBIT. 



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 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 intervertebral liga- 

 ments : the cervical vertebrae are seven in number. The 

 sternum is transversely jointed. In the skull there is a 

 completely ossified occipital ring, with two condyles : the 

 cranial and olfactory cavities are separated by a bony cribri- 

 form 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. The teeth form a single but discontinuous 

 row round the margin of each jaw. In the shoulder girdle 

 the coracoid is reduced to a small process of the scapula, and 

 there is no interclavicle. 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 limb : the preaxial 

 digit, corresponding 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 

 abortive : in other mammals it has two phalanges like the 

 thumb. 



Examine the prepared skeletons and make drawings to scale 

 of the several parts. 



