Bones of the Spine. 71 



Processus spinosus 



Processus articularis inferior 

 Processus articularis superior 

 Processus mamillaris 



Processus accessorius 



Processus transversus 



89. Third lumbar vertebra, vertebra lumbalis III, from above. 



The five yertebrae lumfoales (lumbar vertebrae) (see also Fig. 88) are higher and 

 broader than the cervical and thoracic vertebrae. Their bodies have flat connecting surfaces, 

 varying from a bean -shaped to a transversely oval form. The foramen vertebrale is narrow 

 and triangular. The processus articulares are vertical ; their fades articular es lie nearly in 

 sagittal planes ; the fades articulares superiores are concave behind and hollowed out median- 

 ward, the fades articulares inferiores are convex in front and lateralward, so that the two 

 belong to a cylinder-mantle, the axis of which is situated behind the processus spinosus ; every 

 two processus articulares superiores surround the processus articulares inferiores of the next 

 vertebra above as an axle-box does an axle. On the posterior margin of the processus arti- 

 cularis superior a blunt bony mass, the processus mamillaris, projects backward. The pro- 

 cessus spinosi are flat and high, pass straight backward, end in a swollen extremity and are 

 often bent hook-like, downward. The processus transversi arise in front of the processus 

 articulares ; they are thin, flat and directed only slightly backward. They are considered from 

 their largest part to be homologues of the ribs; the corresponding part is accordingly also 

 designated .as the processus costarius; this is sometimes especially large on the first lumbar 

 vertebra and united by a joint with the rest of the process; it is then called a lumbar rib 

 (see Fig. 96, No. 8). On the posterior surface of the root of the transverse process, lateral 

 from and below the processus mamillaris, a small, variably developed nodule, the processus 

 accessorius, projects backward. 



The fifth lumbar vertebra (see Fig. 96, No. 9) is peculiar in that its body is essentially 

 higher in front . than behind and that its processus transversi are short, thick and bluntly 

 wedge-shaped. 



