DISSECTION OF THE PELVIS. 377 



The bones should be disarticulated to show the articular surfaces. 

 The joint is provided with a rudimentary synovial menihrane. 



Saoro-ooccygbal and Inter-coccygbal Articulations. Ordinarily 

 these are movable joints, the articular surfaces being the opposed 

 extremities of the rudimentary vertebral bodies. These are connected 

 by small intervertebral discs, which are shaped like a biconcave lens, 

 since the bodies of the vertebrse are here convex on both extremities. 



The bones are also invested by a fibrous sheath, which may be 

 supposed to represent the superior and inferior common ligaments of 

 the back and loins. 



Movements. — The biconvex form of the vertebral centra, and the 

 suppression of the different processes in this region give a great range 

 and freedom of movement to the tail, which, provided with its appendage 

 of hairs, is admirably fitted to protect the hind quarters of the animal 

 from the attacks of insects. It is interesting to notice the absence of 

 the panniculus carnosus over the area within which the tail is serviceable 

 for this purpose. In animals above middle age it is not uncommon to 

 find the sacro-coccygeal, and even the first intercoocygeal joint, 

 anchylosed. 



