THE LUMBAR VERTEBRAE 57 



of behind them, as in the thoracic vertebrae, and are homologous with the ribs. Of 

 the three tubercles noticed in connection with the transverse processes of the 

 twelfth thoracic vertebra, the superior one on each side becomes connected in this 

 region with the back part of the superior articular process, and has received the 

 name of mammillary process (processus mammillaris); the inferior is represented 

 by a small process pointing downward, situated at the back part of the base of 

 the transverse process, and called the accessory process (processus accessorius); 

 these are the true transverse processes, which are rudimentary in this region of 

 the spine. The external one, the so-called transverse process, is the homologue 

 of the rib, and constitutes the costal process (processus costarius) (Fig. 22). 

 Although in man the costal processes are comparatively small, in some animals 

 they attain considerable size, and serve to lock the vertebrae more closely together. 



Inferior articular 

 process 



Transverse process 



Mammillary process 

 Accessory process 



Superior articular 

 process 



FIG. 22. Lumbar vertebra, viewed obliquely. 



Fifth Lumbar Vertebra. The fifth lumbar vertebra is characterized by 

 having the body much thicker in front than behind, which accords with the promi- 

 nence of the sacrovertebral articulation; by the smaller size of its spinous process; 

 by the wide interval between the inferior articulating processes; and by the greater 

 size and thickness of its transverse processes, which spring from the body as well 

 as from the pedicles. 



Attachment of Muscles. To the Atlas are attached nine pairs: the Longus colli, Rectus 

 capitis anticus minor, Rectus lateralis, Obliquus capitis superior and inferior, Splenius colli, 

 Levator anguli scapulae, First Intertransverse, and Rectus capitis posticus minor. 



To the Axis are attached eleven pairs: the Longus colli, Levator anguli scapulae, Splenius 

 colli, Scalenus medius, Transversalis colli, Intertransversales, Obliquus capitis inferior, Rectus 

 capitis posticus major, Semispinalis colli, Multifidus spinae, Interspinales. 



To the remaining vertebrae, generally, are attached thirty-five pairs and a single muscle: 

 anteriorly, the Rectus capitis anticus major, Longus colli, Scalenus anticus, medius, and posticus, 

 Psoas magnus and parvus, Quadratus lumborum, Diaphragm, Obliquus abdominis internus. 

 and Transversalis abdominis; posteriorly, the Trapezius, Latissimus dorsi, Levator anguli 

 scapulae, Rhomboideus major and minor, Serratus posticus superior and inferior, Splenius, 

 Erector spinae, Iliocostalis, Longissimus dorsi, Spinalis dorsi, Cervicalis ascendens, Trans- 



