ANATOMY IN A NUTSHELL. 



133 



formed by the laminae and spinous process. The superior articular processes are 

 oval and concave. They are situated on each side of the sacral canal and are 

 directed backward and inward. The intervertebral notches are in front of these 

 processes. 



The al.e are flat triangular areas on each side of the articular processes, 

 and are continuous with the iliac fossa. The Iliacus muscle has a \'v\v fibers of 

 origin from the ala. 



The apex articulates with the coccyx and is directed downward and for- 

 ward. 



PLATE XLVI. 



PROMONTORY. 



ARTIC.WITH 

 LAST LUMBAR. 



COCCYGE 



LEVATOR ANl 



Anterior View of Sacrum and Coccyx. 



The spinal canal is larger and triangular above, but*below it is ilattened 

 from before backward. The lower part of its posterior wall is incomplete. This 

 is caused by the non-development of the laminse and spinous processes. 



Ossification : — Thirty-five centers. 



Articulation: — With four bones; the lasl Lumbar vertebra, coccyx, and 

 the two ossa innominata. 



Attachment of Muscles: — Eight pairs; in front, the Pyriformis and 

 Coccygeus, and a portion of the Iliacus to the base of the bone: behind, the 

 Gluteus maximus, Latissinnis dorsi. Multifidus spinse, and Erector spinae, and 

 sometimes the Extensor coccveeus. 



