54 OUTLINES OF EQUINE ANATOMY. 



vertebrae. The bodies of tbese vertebrae are larger and 

 more prisuiatic than those of the dorsal, terminating iiife- 

 riorly in somewhat marked ridges, inferior spinous pro- 

 cesses, for attachment of the inferior vertebral ligament, to 

 which the crura of the diaphragm are attached. To their 

 lateral surfaces] the psose parvi muscles are attached; their 

 anterior and posterior surfaces present but shallow concavi- 

 ties and convexities. The bodies and foramina magna 

 decrease in height from before backwards ; so at the poste- 

 rior part of the last lumbar the body presents a shallow 

 surface, very much elongated transversely. 



THE SACRUM 



in early life, consists of five distinct vertebrae, which in the 

 adult become firmly united by healthy bony union, whereby 

 a firm basis for attachment of the hind limb is afforded. 

 We therefore shall view it as a single bone, since it acts as 

 such. It is situated at the j^osterior part of the spinal 

 column, between the lumbar and coccygeal vertebrae. It 

 articulates laterally with the venter ilii. It is pyramidal 

 in figure, its base being anteriorly placed ; sometimes it is 

 composed of six bones, in consequence of coalescence of the 

 first coccygeal vertebra with its ajjex. It is a false ver- 

 tebra, as its segments are not capable of moving upon each 

 other. The base presents laterally foramen magnum coming 

 to a point superiorly at the root of the superior spinous 

 process, broad inferiorly. It leads mto a canal which 

 gradually and regularly decreases in size from before back- 

 wards, being extremely small posteriorly. The spinal cord 

 extends into this about as far as opposite the second sacral 

 bone ; the membranes of the cord are continued farther. 

 Below this opening is an articulatory surface, the transverse 

 diameter of which is about twice as long as the vertical ; it 

 is slightly convex in all directions. At the sui3ero -lateral 

 parts of the foramen are the oblique processes, which are 

 roughened externally, and internally present concave facets 

 looking uj^wards and inwards. From the inferior part of 

 the anterior margin of each of these a thin ridge runs to 

 meet its fellow at the root of the superior sj^inous j^rocess 

 of the first bone. Below the oblique processes are the 

 intervertebral notches, which lead into grooves running 

 from the upper to the under surface of the transverse pro- 



