////: III-.AD AND NECK. 151 



plexus. The conservatism of emissary veins is well illustrated in the profuse 

 epistaxis of children, incident to cerebral congestion. In this case an emissary 

 vein connects centrally the blood in the superior longitudinal sinus with the 

 blood in the mucous membrane of the nose ; the latter, being the weaker structure, 

 gives way, and the arterial pressure in the brain is relieved by a profuse hemor- 

 rhage. The emissary foramina seem to belong more especially to the physio- 

 logical needs of childhood. The greater number of emissary veins and their 

 foramina disappear as adult years come on. By osteological classification these 

 foramina are inconstant. 



The following table gives a list of the emissary foramina, the central sinuses, 

 and the peripheral veins, between which the emissary veins stand, holding the 

 two together like the handle connects the two globes of a dumb-bell : 



TABULATED LIST OF EMISSARY STRUCTURES. 



FORAMEN. CENTRAL SINUS. PERIPHERAL VEIN. 



Caecum, Superior longitudinal, Nasal mucous membrane. 



Carotid canal, Cavernous, Internal jugular vein. 



Parietal Lateral, Occipital. 



Vesalii, Cavernous, Internal jugular vein. 



Posterior condylar, Lateral, Deep cervical. 



Occipital Torcular Herophili, Occipital veins. 



Anterior condylar Occipital, Deep cervical. 



Mastoid, Lateral, Occipital veins. 



Sphenoidal fissure Cavernous, Angular and ophthalmic. 



Ovale Cavernous, Pharyngeal and pterygoid. 



How SEFHC THROMBI REACH THE SINUSES. 



Hcnv may a carbuncle of the face, or facial erysipelas, or infection of the scalp 

 over the forehead result in fatal blood-poisoning ? 



Septic thrombi from these sources may reach the cavernous sinus and get 

 beyond the reach of the surgeon. The frontal and supraorbital veins unite to 

 form the angular, and this is one of the large tributaries of the facial vein. 

 (Fig. 1 8.) Now, the angular vein communicates with the ophthalmic. The 

 ophthalmic vein passes through the sphenoidal fissure, and is tributary to the 

 cavernous sinus. The angular, facial, and ophthalmic veins contain no valves, 

 hence the blood can pass either forward or backward from the superficial seat of 

 infection to a region beyond the reach of surgical drainage and antisepsis. 



Tell the course septic material from a carious tooth, alveolar abscess, or suppura- 

 tion of the anlnun follows in cases of fatal blood-poisoning to reach the sinuses in 

 (lie dura mater beyond tlie reach of operative procedure. 



To appreciate an answer to this question you must recall the distribution of the 

 internal maxillary artery to the muscles of mastication, the teeth, the nasal fossae, 

 the meninges, and the palate. Now, the veins returning the blood from these areas 

 take the course of their companion arteries, and the same name as the arteries. 

 The veins from these regions, the small and great meningeal, the supraorbital 

 and posterior dental, the palatine and spheno-palatine, the deep temporal, ptery- 

 goid, and buccal, the lower ophthalmic and Vesalian, all come together on the 

 inner surface of the internal pterygoid muscle to form the pterygoid plexus. 

 This plexus communicates with the cavernous sinus by the Vesalian vein. As 

 these veins contain no valves, septic thrombi originating anywhere in the dental, 

 alveolar, antral, nasal, or palatine regions may spread backward to the cavernous 

 sinus via the Vesalian vein and pterygoid plexus. 



