THE HEAD AND NECK 1261 



part of the outer wall, and the anterior portions of the middle and inferior 

 conchae. The posterior ethmoidal furnishes nasal branches which enter the 

 nasal fossa through some of the foramina in one half of the cribriform plate 

 of the ethmoid bone, and are distributed to the roof and upper part of the 

 septum. 



The superior coronary artery, a branch of the facial, furnishes the artery of the 

 septum, which suppUes the anterior part of the septum and the columella nasi. 



The veins form a copious plexus, especially over the inferior concha and 

 the lower margin and back part of the middle concha. The vessels which 

 carry away the blood from the plexus correspond to the various arteries, and 

 their principal destination is threefold, namely, (i) the pterygoid plexus, 

 (2) the superior ophthalmic vein, and (3) the facial vein. The ethmoidal veins, 

 which open into the superior ophthalmic vein, communicate with the intra- 

 cranial anterior meningeal veins and with the angular vein of the face by 

 means of twigs which pass through minute apertures in the nasal process of 

 the superior maxilla, and, it may be, through a small foramen in the nasal 

 bone. In those cases where the foramen caecum is pervious it transmits an 

 emissary vein which passes between the intracranial superior longitudinal 

 sinus and the veins of the roof of the nasal fossa. 



The lymphatics of the atrium and vestibule pass to the submaxillary lym- 

 phatic glands. The principcd l)anphatics pass to (i) the retro -pharyngeal 

 glands; (2) the deep facial, or internal maxillary, glands; and (3) the superior 

 deep cervical glands. The lymphatics of the air-sinuses end in a simila r 

 manner. 



The lymphatics of the nasal fossae communicate with lymphatic spaces 

 which are related to the olfactory nerve-filaments ; and these lymphatic spaces 

 in turn communicate with the intracranial, subdural, and subarachnoid spcices. 



Development of the Nose. 



The primitive oral cavity, or stomodaeum, becomes divided into two cham- 

 bers, upper or nasal, and lower or oral, this division being effected by the 

 formation of the hard palate. The oral chamber constitutes the permanent 

 mouth, and the nasal chamber becomes transformed into the two nasal fossae. 



The first indications of the olfactory organ are the two olfactory areas. 

 They consist of thickened ectoderm, and are placed on the ventral aspect of 

 the anterior cerebral vesicle, on either side of the mesial nasal process of the 

 fronto-nasal process, and on the cephaUc side of the orifice of the stomodaeum. 



Each olfactory area soon becomes depressed and forms the olfactory pit. 

 The two pits, right and left, are situated one on each side of the mesial nasal 

 process of the fronto-nasal process. Each pit has the corresponding globular 

 process of the mesial nasal process internally, and the lateral nasal process 

 externally, this position corresponding to the situation of the future anterior 

 nans on either side. At this stage the olfactory pits communicate with the 

 stomodaeum, and the orifice of each pit constitutes the corresponding primitive 

 anterior naris. 



The lateral nasal process of the fronto-nasal process is at first separated 

 from the maxiUary process by a groove, called the oculo-nasal, naso-optic, 

 or lachrymal sulcus, which extends from the ocular pit on the outer side of 

 the lateral nasal process (which forms the aJa of the nostril) to the olfactory 

 pit. This sulcus indicates the position of the future lachrymal sac and nasal 

 duct of the corresponding side. When the maxillary process (previously 

 joined by the lateral nasal process) grows inwards to unite with the globular 

 process, it lies below the olfactory pit. In this manner the orifice of the 

 olfactory pit — namely, the primitive anterior naris — is cut off from com- 

 munication with the stomodaeum. 



The blind olfactory pits now grow dorsalwards along the roof of the stomo- 

 daeum, and so give rise to the nasal sacs which represent the primitive nasal 

 fossae. As each pit grows dorsalwards it is deepened by the formation of a 

 groove, called the nasal groove, which extends to the roof of the stomodaeum. 

 This groove is bridged over by ectoderm, and is thus separated from the 

 corresponding olfactory pit. VVhen the maxillary process (previously joined 



