THE EXTERNAL CAROTID ARTERY 603 



The anterior tympanic branch (a. tympanica anterior} passes upward behind 

 the articulation of the mandible, enters the tympanum through the Glaserian 

 fissure, and ramifies upon the membra na tympani, forming a vascular circle 

 around the membrane with the stylomastoid artery, and anastomosing with the 

 Vidian and the tympanic branch from the internal carotid. 



The deep auricular branch (a. auricularis pro/undo) often arises in common 

 with the preceding. Tt ascends in the substance of the parotid gland, behind the 

 temporomaxillary articulation, pierces the cartilaginous or bony wall of the external 

 auditory meatus, and supplies its cuticular lining and the outer surface of the 

 tympanic membrane. It gives a branch to the temporomandibular joint. 



The middle meningeal or medidural branch (a. mcningea media, a. mediduralis) is 

 the largest of the branches which supply the dura. It ascends between the internal 

 lateral ligament and the neck of the mandible, and passes vertically upward between 

 the two roots of the auriculotemporal nerve to the foramen spinosnm of thp sphp- 

 noid bone, through which it enters the cranium; it then runs upward and forward 

 in a groove on the greater wing of the sphenoid bone and divides into two branrhps 

 jtnterior and posterior. The anterior branch, the larger, crosses the greater wing 

 of the sphenoid, and reaches the groove, or canal, in the antero-inferior angle of 

 the parietal bone, and then divides into two branches which spread out between the 

 dura and internal surface of the cranium, some passing upward as far as the ver- 

 tex, and others backward to the occipital region. The posterior branch crosses the 

 squamous portion of the temporal, and on the inner surface of the parietal bone 

 divides into branches which supply the posterior part of the dura and cranium. 

 The branches of this vessel are distributed partly to the dura, but chiefly to the 

 bones; they anastomose with the arteries of the opposite side, and with the anterior 

 and posterior meningeal arteries. 



The middle meningeal on entering the cranium gives off the following collateral branches: 

 (1) Numerous small vessels to the Gasserian ganglion, and to the dura in this situation. (2) 

 A branch, the petrosal branch (ramus petrosus superficialis}, which enters the hiatus Fallopii, 

 supplies the facial nerve, and anastomoses with the stylomastoid branch of the posterior auricular 

 artery. (3) A minute superior tympanic branch (a. tympanica superior}, which runs in the 

 canal for the Tensor tympani muscle, and supplies this muscle and the lining membrane of the 

 canal. (4) Orbital branches, which pass through the sphenoidal fissure, or through separate 

 canals in the greater wing of the sphenoid to anastomose with the lacrimal or other branches of 

 the ophthalmic artery. (5) Temporal or anastomotic branches, which pass through the fora- 

 mina in the greater wing of the sphenoid bone and anastomose in the temporal fossa with the 

 deep temporal arteries. 



Applied Anatomy. The middle meningeal is an artery of considerable surgical importance, 

 as it may be injured in fractures of the temporal region of the skull. The vessel may be ruptured 

 by traumatism, even though the skull escape fracture. Rupture of the middle meningeal artery 

 will be followed by considerable, hemorrhage between the bone and dura, which may cause 

 compression of the brain and require the operation of trephining for its relief. This artery 

 crosses the anterior inferior angle of the parietal bone at a point 1 inches (3.75 cm.) behind 

 the external angular process of the frontal bone, and If inches (4.5 cm.) above the zygoma. 

 From this point the anterior branch passes upward and slightly backward to the sagittal suture, 

 lying about \ inch (12 mm.) to f inch (18 mm.) behind the coronal suture. The posterior 

 branch passes upward and backward over the squamous portion of the temporal bone. In 

 order to expose the artery as it lies in the groove in the parietal bone, a semilunar incision, with 

 its convexity upward, should be made, commencing an inch behind the external angular process, 

 and carried backward for two inches. The structures cut through are: (1) Skin; (2) superficial 

 fascia, with branches of the superficial temporal vessels and nerves; (3) the fascia continued 

 down from the aponeurosis of the Occipitofrontalis; (4) the two layers of the temporal fascia; 

 (5) the Temporal muscle; (6) the deep temporal vessels; (7) the pericranium. The bone is 

 trephined, the clot removed, and the vessel secured by ligatures, suture ligatures, or gauze 

 packing. 



The small meningeal or parvidural branch (ramus meningeus accessorius, parvi- 

 duralis) is sometimes derived from the preceding. It enters the skull through the 

 foramen ovale, and supplies the Gasserian ganglion and dura. 



