ANATOMY IN A NUTSHELL. 443 



(11) Obex is a band of gray nervous matter at the point of the calamus 

 soriptorius. The calamus scriptorius is the groove on the floor of the fourth 

 ventricle, at the end of which is the Ventricle of Arantius. 



(12) Ligula is the tongue shaped organ of white matter on the lower part 

 of the roof of the fourth ventricle. 



(13) Fovea superior is a depression in the floor of the fourth ventricle 

 on the outer side of the eminentia teres. 



(14) Fovea inferior is a depression with its apex at the striae, which 

 cross the center of the floor of the fourth ventricle, and its base below. 



(15) Eminentia teres is on each side of the median line on the upper 

 half of the floor of the fourth ventricle. It is produced by an underlying bundle 

 of white fibers (funiculus teres) formed by fibers of the facial nerve. 



(16) Conductor sonorus is formed by a whitish band of fibers which are 

 connected below with the strke medullaris. 



(17) Ala cinerea (trigonum vagi) is a d< pr< ssion below the inferior fovea. 



(18) Trigonum hypoglossi is situated on the inner side of the inferior 

 fovea. 



(19) Tuberculum acusticum is situated en the outer side of the inferior 

 fovea. 



(20) Fasciculus unciformis connects the parietal lobe with the temporal 

 lobe, and is situated in the bottom of the fissu'-e of Sylvius. 



(21) Locus ceruleus is a bluish depression above the fovea superior. 



LESSON CXXXVI. 



The relations of the External Carotid Artery. (Plates CXVI- 

 CXVII-CXVIII. 



In Front. — (1) Skin. (2) Superficial fascia. (3) Platysma and deep fascia. 

 (4) Anterior border of Sterno-mastoid, (•">) Hypoglossal nerve, (6) Lingual 

 vein, (7) Facial vein, (8) Digastric muscle. (9) Stylo-hyoid muscle. (10) 

 Parotid gland with facial nerve and temporo-maxillary vein in its substance. 



Behind. — (1) Superior laryngeal nerve, (2) Stylo-glossus, (3) Stylo? 

 pharyngeus, (4) Glosso-pharyngeal nerve, (5) Parotid "land. 



Externally. — Internal carotid artery. 



[nternally. — (1) Hyoid bone, (2) Pharynx, (3) Superior laryngeal 

 nerve, (4) Parotid gland, (5) Ramus of jaw. 



The INTERNAL CAROTID ARTERY (PlaKs CXVI-CXVII-CXVIII) which 



begins at the upp< r border of the thyroid cartilage is divided for convenience 

 into four parts. (1) The cervical portion passes vertically upward in front of 

 the transverse processes of the three upper cervical vertebra? to enter the car- 

 otid canal in the petrous portion of the temporal bone. This portion has no 

 branches. (2) The petrous portion passes in the carotid canal where it runs 

 forward and inward in front of the tympanum and from here ascends to the 

 cavernous sinus. This portion gives off the tympanic branch, which runs 

 through a small foramen in the wall of the carotid canal to enter the tympanum. 

 (3) The cavernous portion passes in the cavernous sinus to the posterior clinoid 

 process and from here along the body of the sphenoid bone and then passes 



