40 



THE SKELETON OF THE HOESE 



is thick, the lateral part thinner, narrower, and curved forward. The medial part 

 of the fifth is also somewhat thickened. Medial to the articular surfaces the edges 

 of the transverse processes are cut into by notches, which form foramina by apposi- 

 tion with each other and the sacrum. 



The spinous processes resemble those of the last two thoracic vertebrae. 



Spinous process 



Mammillary process 

 Articular process 



TruNsptrse jtroci'ss 



Ventral spine 

 Fig. 16. — Second Lumbab Vertebr.4. of Horse; Posterior View. 



They are usually about equal in height, but minor differences are common, and the 

 width diminishes in the last three. 



Development. — This is similar to that of the thoracic vertebrae. The extremi- 

 ties of the transverse processes remain cartilaginous for some time after ossification 

 is otherwise complete. 



The transverse processes of this region are considered equivalent to the proper transverse 

 process + the costal element, and hence the distinctive term processus lateraUs (s. costarius) 



« 



Spinous process 



1 'erlebral foramen 



\ Articular processes 



Transverse process 



Xotch 



Body 



Articular surface for 

 wing of sacrum 

 Fia. 17. — Last Lumbar Vertebra of Horse; Posterior View. 



has been proposed. The occurrence of a rib in cormection with the transverse process of the first 

 lumbar vertebra is common. Reduction of the number to five has been observed frequently and 

 may or may not be compensated by an additional thoracic vertebra. Very few cases are recorded 

 of se\'en lumbar vertebrse — especially with the normal thoracic number. An anomalous ^'ertebra 

 with mixed thoracic and lumbar characters sometimes occurs at the junction of the two regions. 



