106 OSTEOLOGY. 
occipital foramen or foramen magnum. The expanded curved plate behind the 
foramen is the tabular or squamous part. The thick rod-like portion in front of the 
foramen is the basilar process. (n either side the foramen is bounded by the 
lateral or condylic portions. 
The tabular or squamous part (squaima occipitalis) in shape somewhat resembles 
a Gothic arch, and is curved from side to side and from above downwards. It forms 
inferiorly a small portion of the middle of the posterior boundary of the foramen 
magnum, and unites on either side of that with the lateral parts of the bone. About 
the centre of the external surface of the squama there is a prominence—the external 
occipital protuberance (protuberantia occipitalis externa), which varies considerably 
in its distinctness and projection, and serves for the attachment of the ligamentum 
nuche. From the protuberance on either side two lines curve out towards 
the external angles of the bone. These are known respectively as the highest and 
External occipital protuberance 
Highest curved line 
Superior curved line 
Inferior Sree 
curved ae ee 
line - 
Jecipitalis 
~ Sterno-mastoid 
Rect. cap. 
post. min. 
Splenius 
capitis 
Rect. cap. 
post. maj. 
Obliquus 
Ext.occipital superior 
Posterior con- Gnest 
dylic foramen 
Foramen 
~~ Rect. cap. lateralis 
Jugular note =a 
Ye 
Condyle/ Rect. cap. ant. min. 
—— Rect. cap. ant. maj. 
Pharyngeal tubercle —— 
Superior constrictor 
Fic. 82.—OcctpITaAL BONE AS SEEN FROM BELOW. 
superior curved lines (linea nuchze suprema and linea nuchiw superior). To the 
upper of these the epicranial aponeurosis is attached, whilst the lower serves for 
the origin of the trapezius and occipitalis muscles and the insertion of the sterno- 
mastoid and splenius capitis muscles. The two lines together serve to divide the 
external surface of the tabular part into an upper or occipital portion (planum 
occipitale), covered by the hairy scalp and a lower or nuchal part (planum nuchale) 
serving for the attachment of the fleshy muscles of the back of the neck. Asa rule 
the occipital part bulges backwards beyond the external occipital protuberance ;. 
exceptionally, however, the latter process is the most outstanding part of the bone. 
The nuchal plane, irregular and rough, is divided into two lateral halves by a 
median ridge—the external occipital crest (linea nuchze mediana), which stretches. 
from the external occipital protuberance above to the posterior border of the foramen 
magnum below. Crossing the nuchal plane transversely, about its middle, is the 
inferior curved line (linea nuche inferior), which passes outwards and forwards on 
either sidé towards the lateral margins of the bone. The areas thus marked out 
