26 PRACTICAL ANATOMY. 



into the tympanum. The quadrilateral rough surface 

 affords attachment to muscles. The aquseductus cochlea 

 transmits a vein from the cochlea, and frequently a small 

 artery is seen entering the canal by the side of the vein. 

 The jugular fossa is deep, and, with the jugular notch 

 on the occipital bone, forms the jugular foramen. The 

 carotid canal passes vertically upward one-fourth inch, 

 then bends at right angles, runs horizontally forward for 

 another fourth of an inch, and terminates at the apex. 

 That part of the anterior surface of the petrous portion 

 overlying the carotid canal is notched for the passage of 

 the artery upward to the base of the brain. A vertical, 

 antero-posterior section of the petrous portion shows 

 that it approaches an equilateral triangle. Its superior 

 border is grooved for the lodgment of the superior 

 petrosal sinus and for the attachment of the tentorium 

 cerebelli. The petrous portion does not contain any 

 spongy tissue. In it is found an excess of the mineral 

 matter. The temporal bone is developed by two prin- 

 cipal centres, one for the zygomatic and squamous part, 

 and the other for the petrous and mastoid portion. The 

 styloid process and the auditory process have each a 

 separate centre. These centres appear near the end 

 of the second month. The temporal bone contains the 

 organs of hearing, which will be described with the ear. 



THE SPHENOID BONE. 



The sphenoid bone is situated at the base of the 

 skull. It articulates with the orbital plates of the 

 frontal anteriorly, and with the basilar process of the oc- 

 cipital posteriorly. It also articulates with all the other 

 bones of the cranium, binding them firmly and solidly 

 together, and with five bones of the face, the two malar, 

 the two palate, and the vomer. It presents for exam- 



