THE CRANIUM. 



21 



frontal suture, the numerous Wormian bones in the lambdoid suture, the so-called fontanelle- 

 bones occurring in the paired and in the single fontanelles, and the interparietal bone, which corre- 

 sponds to that portion of the occipital bone which is laid down in membrane. 



The base of the skull is formed by the following bones: The frontal, the ethmoid, the 

 sphenoid, the temporal, and the occipital. 



The points of exit o) the twelve cranial nerves from the base of the skull (indicated in Plate 

 i by yellow) are: (i) The cribriform plate of the ethmoid which lodges the olfactory bulb and 

 which gives passage to the olfactory filaments on their way to the nasal fossa. (2) The optic 

 foramen for the optic nerve (and the ophthalmic artery arising from the internal carotid). (3) 

 The sphenoidal fissure for the oculomotor, trochlear, ophthalmic division of the fifth, and the 

 abducent nerves. (4) The foramen rotundum for the superior maxillary division of the fifth 

 nerve. (5) The foramen ovale for the inferior maxillary division of the fifth nerve. (6) The 



Sagittal suture 



Parietal bone-- 



Occipital fontanelle 



Occipital bone- 



Lambdoid suture- 



Posterolateral fontanelle- 



Frontal fontanelle 



Frontal bone 

 -Coronal suture 



- Anterolateral fontanelle 



~~ Great wing of sphenoid 



a _ Squamous portion of 



temporal bone 

 Zygoma 



Lower maxilla 



Mastoid portion of tem- 

 poral bone 



FIG. 5. The skull of the new-born seen from above and behind. 



internal auditory meatus for the facial and auditory nerves. (7) The jugular foramen, anterior 

 portion, for the glossopharyngeal, vagus, and spinal accessory nerves [in the order named from 

 before backward between the inferior petrosal sinus in front and the lateral sinus behind. 

 ED.]. (8) The anterior condyloid foramen for the hypoglossal nerve. 



The points of entrance of the main arteries (designated in Plate i by red) are : (a) To the brain : 

 The foramen magnum for the two vertebral arteries (n) from the subclavian, and the carotid 

 canal in the petrous portion of the temporal bone for the internal carotid (9). (b) To the dura 

 mater, i. e., to the internal periosteum of the cranial vault and to the vault itself: The foramen 

 spinosum in the great wing of the sphenoid for the middle meningeal branch of the internal max- 

 illary artery (10). 



The venous blood from the brain is collected in the cerebral sinuses and leaves the cranial 



