66 PRACTICAL ANATOMY. 



transverse diameter of the skull. It is bounded pos- 

 teriorly by the occipital bone, anteriorly by the petrous 

 portion of the temporal. It is formed by the jugular 

 notch of the occipital and jugular fossa of the temporal 

 bone. Its axis is curved, being directed at first upward, 

 then horizontally backward. It transmits the jugular 

 vein, the glosso-pharyngeal, pneumogastric, and spinal 

 accessory nerves. External to the jugular foramen is 

 the stylo-mastoid foramen, out of which the facial nerve 

 emerges from the skull. Anterior to the jugular foramen 

 is the opening of the carotid canal, which at first passes 

 vertically upward, then horizontally inward and forward; 

 its upper inner wall is deficient. In front of the carotid 

 foramen, in the angle between the petrous and squamous 

 portions of the temporal bone, is the rough, funnel- 

 shaped opening of the Eustachian canal, which leads into 

 the tympanum ; it is directed obliquely backward and 

 outward and is divided horizontally by a partition of 

 bone, the processus cochleariformis. The lower part 

 of the canal serves as an air-vent (it is the Eustachian 

 canal proper) to the tympanum. The upper canal lodges 

 the laxator tympani muscle. 



In front of the foramen magnum is the rough quad- 

 rilateral basilar process, continuous in the adult skull 

 with the body of the sphenoid, with which it joins just 

 behind the vomer. The sides of the basilar process 

 assists in forming the middle lacerated foramen, which 

 is bounded externally by the apex of the petrous portion 

 of the temporal bone, anteriorly by the base of the 

 pterygoid process and posterior border of the great wing 

 of the sphenoid, and internally by the basilar process of 

 the occipital. It is triangular, with the base of the tri- 

 angle directed forward, and in the recent state is filled 

 with cartilage, which, however, is penetrated by small 



