SACRUM. 



11 



ridges, which indicate the places of union of the bodies of the five vertebra ; 



and at the extremities of these ridges are situated on each side four foia- 



mina called anterior sacral, which transmit 



the anterior divisions of the sacral nerves. 



These foramina are sloped externally into 



grooves, and diminish gradually in size from 



above downwards. 



Fig. 8. SACRUM OP THE MALE, VIEWED FROM 



BEFORE, -j 



1, 1, four transverse ridges, indicating the place of 

 original separation of the bodies of the five sacrul 

 vertebrae; 2, anterior sacral foramina; 3, 4, lateral 

 surface ; 5, a notch which, with the coccyx, forms a 

 passage for the filth sacral nerve ; 6, oval surface of 

 the upper part of the sacrum for articulation with the 

 body of the last lumbar vertebra; 7, superior articular 

 processes ; 8, inferior oval surface fur articulation with 

 the coccyx ; +, inferior lateral angle. 



The dorsal surface is convex, very uneven, and somewhat narrower than 

 the pelvic surface. It presents along the median line four small eminences, 

 the spinous processes, usually more or less connected, so as to form a ridge. 

 Below the last spinous process is a triangular opening, the termination of 

 the spinal canal, the lateral margins of which are formed by the imperfect 

 laminae of the fifth sacral vertebra, and present a pair of tubercles, the 

 sacral cornua, which project downwards, and articulate with the cornua or 

 horns of the coccyx. On each side of the ridge of spines the surface is 

 smooth and hollowed in the position of the united laminae, and beyond this 

 surface are two rows of eminences, the inner of which corresponds with the 

 articular and mammillary processes of the lumbar vertebrae, while the outer 

 ranges with the transverse processes. In the groove between the two rows 

 are placed the four posterior sacral foramina, which are smaller than the 

 anterior, and transmit the posterior divisions of the sacral nerves. 



The lateral aspect or border presents anteriorly a large uneven surface, 

 covered in the recent state with cartilage, which articulates with the ilium, 

 and is called from its shape the auricular surface : behind this it is rough 

 and very uneven for the attachment of the posterior sacro-iliac ligaments. 

 Lower down, the margin of the sacrum is thin and sinuous, giving attach- 

 ment to the sacro-sciatic ligaments, and terminates in the inferior lateral 

 angle; below which the breadth of the bone is suddenly contracted, so 

 that with the adjacent part of the coccyx a notch is formed for the trans- 

 mission of the fifth sacral nerve. 



Fig. 9. UPPER SURFACE OR BASE OF THE 

 SACRUM OF A MALE, TO COMPARE WITH 

 FIG. 3, A, OF THE LUMBAR VERTEBRA. 



1, the body ; 4, the foramen, ring, or sacral 

 canal; 5, the spinous process of the first sacral 

 vertebra ; 6, the part corresponding to a 

 transverse process, in front of which is the 

 lai'ge lateral mass ; 7, the superior articulat- 

 ing process ; 7', the inferior articulating pro- 

 cess ; e, the mammillary tubercle; /, the 

 accessory tubercle, slightly seen. 



The base, looking upwards and forwards, presents in the middle an oval 



