174 



MAMMALIAN ANATOMY 



FIG. 113. 



jugular process, in the interval between the conclyle and the root of 

 the basilar process. 



The inner part of the lower edge of the jugular process, near the 

 condyloid foramen, is often incised ; more rarely at this point is a 

 small antero-posterior canal. 



HUMAN OCCIPITAL BONE. 



In the human occipital bone the basilar process is relatively 

 smaller, and the occipital plate, which is oval in outline, is bowed 

 strongly forward. 



On the external surface (Fig. 113), near the middle, is the ex- 

 ternal occipital protuberance, from which the superior curved line 



arches outward on each side to the lateral 

 angle. The area above the line is smooth 

 and faces upward and backward ; it is 

 developed in membrane as a distinct bony 

 element, and corresponds, in part at least, 

 to the interparietal of the cat. Traces of 

 the original occipito-interparietal suture 

 are sometimes found in adult bones, most 

 frequently as incisions in the borders. 

 The area is marked by two obscure 

 highest lines passing forward and out- 

 ward from the protuberance to the ante- 

 rior border. The area below the pro- 

 tuberance is a continuation backward and 

 upward of the base of the skull. It 

 exhibits the median external occipital 

 crest, from the middle point of which 

 the inferior curved lines arch downward, outward, and forward toward 

 the jugular processes. 



The lateral border, between the lateral angle and the jugular 

 process, is sometimes incised at the point which marks the end of the 

 original suture between the supraoccipital and the exoccipital. 



Each jugular process is small, and its intracranial surface is 

 marked by the lower part of the lateral sinus. Inasmuch as there 

 is no auditory bulla on the human temporal bone, the temporal 

 articular surfaces of the jugular process are less extensive. 



OCCIPITAL BONE. EXTERNAL VIEW. 



1, superior curved line; 2. external oc- 

 cipital protuberance ; 3, external occipital 

 crest; 4, inferior curved line; 5, occipital 

 foramen; 6, condyle; 7, fossa behind the 

 condyle, into which the posterior con- 

 dyloid foramen frequently opens; 8, posi- 

 tion of anterior condyloid foramen; 9, 

 jugular process; 10, notch contributing to 

 form the jugular foramen; 11, basilar 

 process. 



