OLFACTORY NERVES. 673 



Dissection. At this stage of the dissection, but little will be Dissection 

 seen of the distribution of the olfactory nerves. If the bony and andTesseis. 

 cartilaginous septum be removed, so as to leave entire the membrane 

 covering it on the left side, the nervous filaments will appear on 

 the surface, near the cribriform plate. In the membrane, near the 

 front of the septum, an offset of the nasal nerve is to be found. 



The naso-palatine nerve and artery (fig. 238, 3 ) are to be sought 

 lower down, as they are directed from behind forwards, towards 

 the anterior palatine fossa ; the artery is readily seen, especially if 

 it is injected, but the fine nerve is embedded in the membrane, and 

 will be found by scraping with the point of the scalpel. 



By cutting through the fore and upper part of the membrane 

 detached from the septum nasi, other branches of the olfactory 

 nerve may be traced on the outer wall of the nasal fossa. 



The OLFACTORY NERVES spring from the under surface of the Olfactory 

 olfactory bulb as it lies on the cribriform plate of the ethmoid bone nerves : 

 (fig. 238, J ), and descend to the olfactory region of the nose through 

 the apertures in this part of the roof. They are about twenty in 

 number, and are divided into two sets. Those of the inner set are inner set; 

 the larger, and run downwards in the grooves on the perpendicular 

 plate of the ethmoid, to be distributed over the upper third of the 

 septum. The outer set (fig. 239, p. 675) ramifies over the upper 

 turbinate bone, the flat surface of the ethmoid in front of this, and outer set. 

 the fore part of the middle turbinate bone. As the nerves leave the 

 skull, they receive sheaths from the dura mater and pia mater, which 

 are continued as far as their terminal ramifications, and then become 

 lost in the surrounding tissue. The trunks break up into tufts of 

 filaments which communicate freely together, forming a close net- 

 work beneath the mucous membrane. The olfactory nerves consist 

 wholly of non-medullated fibres. 



The other nerves in the nose will be described in the following 

 section. 



Blood-vessels. The different vessels of the nose will be described Biood-ves- 

 in the next section, p. 677 et seq. The artei'ies form a network in ^ 

 the pituitary membrane, and a large submucous plexus on the edge 

 of each of the two lower spongy bones, especially on the inferior. 

 The veins have a plexiform disposition like the arteries, and this veins, 

 is largest on the lower spongy bone and the septum nasi. 



SECTION XIII. 



SPHE SO-PALATINE AND OTIC GANGLIA, THE FINAL 

 BRANCHES OF THE INTERNAL MAXILLARY VESSELS, 

 THE FACIAL NER\ 7 E AND THE INTERNAL CAROTID 

 ARTERY IN THE TEMPORAL BONE. 



The preparation of Meckel's ganglion and its branches (fig. 239), Meckei's 

 and of the terminal branches of the internal maxillary artery, is gang lon ' 

 a difficult task, in consequence of the nerves and vessels being 



D.A. X X 



