68 



ANATOMY FOR NURSES 



[Chap. V 



It occasionally happens that the arch of one of the vertebrae 

 does not develop properly, and as a result the membranes and 

 fluid of the spinal cord will protrude, forming a tumor upon the 

 child's back. This condition is called spina bifida. 



Sacrum (os sacrum). — The sacrum is formed by the union 

 of the five sacral vertebrae. It is a large triangular bone situated 

 like a wedge between the coxal bones, and is curved upon itself 

 in such a way as to give increased capacity to the pelvic cavity. 



Coccyx (os coccygis). 

 — The coccj'x is usually 

 formed of four small seg- 

 ments of bone, and is the 

 most rudimentary part 

 of the vertebral column. 



THORAX 



The thorax is an elon- 

 gated bony cage formed 

 by the sternum and cos- 

 tal cartilages in front, 

 the twelve ribs on each 

 side, and the bodies of 

 the twelve thoracic ver- 

 tebrae behind. It con- 

 tains and protects the 

 principal organs of res- 

 piration and circulation. 



Sternum, or breast 

 bone. — It is a flat, nar- 

 row bone about six inches 

 long, situated in the 

 median line in the front 

 of the chest, and may be 

 likened to a short, flat 

 sword. It consists of 

 three portions. The up- 

 per part is termed the 

 handle, or manubrium ; 

 the middle and largest 



Fig. 46. — The Sternum. Ventral aspect. 

 (Gerrish.) 



