OSTEOLOGY 29 



temporal wings, or ala temporales. The temporal wing forms a 

 cover for the Eustachian tube trumpet, and for the canal coming 

 from the sella turcica, which latter gives passage to the intracranial 

 ca,rotid artery. The orbital wing forms the lower portion of the 

 posterior wall of the orbital cavity, and lies directly before the os 

 petrosum or temporal bone where the second and third branches 

 of the fifth pair of cranial nerves emerge from the cranial cavity. 



Anteriorly the sphenoid has a foramen for the passage of the 

 Eustachian tube, the tuba attditiva, and also a sharp-pointed projec- 

 tion, the nasal portion, called the rostrum. 



The Frontal. Location. — ^The frontal bones, or ossa fron tales, two 

 in number, form the forehead, a portion of the nose, and a portion 

 of the roof of the orbital cavities. They are related posteriorly with 

 the parietal, laterally with the temporal and zygomatic, and ante- 

 riorly with the nasal and premaxillary. They touch inf eriorly the 

 ethmoid. 



Description. — ^Each of these bones has a processus orbitalis which 

 is seen at the outer margin of the posterior and upper orbital wall 

 and just in front of the zygomatic process of the squamous 

 portion of the temporal. The frontal bone forms the anterior 

 portion of the superior wall of the cranial cavity. The two bones are 

 thin, flat, and meet at the median line of the forehead. The external 

 surface is convex. The inner surface has a ridge located longitudi- 

 nally and in the center the bone becomes narrow anteriorly. 



The Parietal. Location. — The parietal bones, or ossa parietalia, 

 two in number, form the posterior part of the roof of the cranial 

 cavity. They meet in the median line and are related posteriorly 

 with the occipital, anteriorly with the frontal, and laterally with the 

 temporal bones. 



Description. — The parietal bones are short and very broad (Fig. 

 5, Part II, No. 8). Each bone is quadrilateral in outline and has 

 two surfaces, four borders and four angles. The external parietal 

 surface is convex and smooth and the internal, cerebral surface is 

 concave. 



The Temporal. Location. — The temporal bones , or ossa temporales, 

 two in number, are located at the lateral portion of the cranium, and 

 aid in the formation of the cra,nial wall. The temporal bone is related 

 posteriorly with the occipital, superiorly with the parietal and fron- 

 tal, externally with the quadratus, anteriorly with the ethmoid, and 

 inferiorly with the sphenoid. 



