SURFACE OF THE CRANIUM. 159 



the internal occipital protuberance. On either side of this gut- 

 ter are the arborescent channels, made by the great middle ar- 

 tery of the dura mater. In this section, we also see the inter- 

 nal face of the os fronlis, excepting its orbitar processes; the 

 parietal bones; and the superior fossae in the occipital bone, for 

 the posterior lobes of the cerebrum. 



The Base of the cranium internally presents a very unequal 

 surface, abounding in deep depressions, processes, and foramina. 

 On its middle line, extending from before backwards, the follow- 

 ing objects should be remarked. The foramen coscum at the 

 front of the crista galli; and, at either side of the latter, the eth- 

 rnoidal gutter, perforated with holes. These gutters are bound- 

 ed, laterally, by the internal margin of the orbitar processes of 

 the os frontis, and behind by the sphenoid bone. At the fore 

 part of the gutter is the oblong foramen for transmitting to the 

 nose the internal nasal nerve, and about half an inch behind this 

 foramen, in the suture, with the os frontis, is the inner orifice 

 of the foramen, called the anterior internal orbitar, which leads 

 the same nerve from the orbit. Immediately behind the ethmoi- 

 dal fossae the sphenoid bone presents a plane surface, upon which 

 are placed the olfactory nerves and the contiguous part of the 

 brain. Behind this plane is the fossa, running from one optic 

 foramen to the other, for lodging the optic nerves. Behind this, 

 again, is the sella turcica or pituitary fossa, bounded at its two 

 anterior angles by the anterior clinoid processes, and behind by 

 the posterior clinoid process. Posterior to the latter is a plane 

 square surface of the sphenoid bone, continuous with the inter- 

 nal surface of the cuneiform process of the os occipitis. On 

 the latter is the depression called basilar gutter, for receiving the 

 medulla oblongata, and which is bounded below by the great 

 occipital foramen. From this foramen to the internal occipital 

 protuberance, proceeds the inferior limb of the occipital cross. 



On both sides of the ethmoidal bone is a convex surface ; called, 

 however, the anterior fossae of the base of the cranium, and 

 formed by the orbitar processes of the os frontis and the little 

 wings of the sphenoid bone, for lodging the anterior lobes of the 

 brain. This surface is terminated behind by the rounded edge 

 of the little wings, which is received into the fissure between the 



