16 



THE SKELETON 



processes. The first pair are large for tlie last lumbar vertebra, the second and 

 third are small, and the fourth and fifth are inconspicuous. 



Inmu'diatelv external to the articular processes are the posterior sacral 

 foramina, four on each side; thev are smaller than the anterior, and give exit to 

 the postin-ior divisions of the first four sacral nerves. External to the foramina 



18.— The Sacrum. (Posterior view.) 



ARTICULAR PROCESS 



AURICULAR SURFACE 



ARTICULAR PROCESS 

 TRANSVERSE PROCESS 



SACRAL FORAMEN 



HIATUS SACRALIS 



LEADING INTO THE 



SACRAL CANAL 



SACRAL CORNU 



SPINOUS PROCESS \C-^ »k % 

 Latissimus dorsi ~^iX| pTj 



Multifldus spinae 



Erector spinae 



Qluteus mazimus 



NOTCH FOR FIFTH SACRAL NERVE 



there are five eminences on each side, representing the fused transverse processes. 

 The first pair are large and conspicuous, and all give attachment to ligaments and 

 muscles; the second form part of the articular surface for the ilium. The furrow 

 formed by the laminae, and bounded on the median aspect by the spinous, and 



Fig. 19. — Base of Sacrum. 



ARTICULAR PROCESS 



LAMINA 



SACRAL CANAL 





■¥ 



f^^> .'^K ^'"^l 



externally l)y the articular processes, is known as the sacral groove, and it lodges 

 th<' iiinltifidiix spin^T iiiusclo. 



The up[)cr surface, or base, of the sacrum rcsenil)les the corresponding aspect 

 of a lumbar vertebra, and its articular processes have well-marked mammillary 

 tul)ercles. The conjoint transverse and costal processes form on each side a broad 

 surface, the wing or ala. From ils margin the i{iaca--i has a small point of origin. 



