144 



THE NOSE. 



nasal cavity and has numerous glands opening into it, is the homologue of a much 

 more extensively developed tubular organ which opens in a similar position m many 

 quadrupeds, and is encircled by a special curved plate of cartilage which lies below 

 the septal cartilage on either side and is known as the cartilage of Jacobson. This 

 is only represented in man by a narrow shred of cartilage (the vomerine cartilage 

 of Huschke), which lies wholly below the rudimentary organ of Jacobson. In the 

 rabbit and guinea-pig as shown by Klein, arid probably in other animals in which 

 the organ is in a well-developed condition, the epithelium which lines the inner or 

 mesial side of the canal is much thicker than that on the outer side. It is throughout 

 similar in structure to that lining the olfactory part of the Schneiderian membrane. 

 Moreover it receives considerable branches of the olfactory nerve, and in these 

 animals is no doubt of high functional importance as an accessory to the proper 

 organ of smell. In man the epithelium on the mesial wall of the canal is thick like 

 the olfactory epithelium, but contains no true olfactory cells. Most of the cells are 

 of the columnar (sustentacular) type, and although there are some more slender 

 spindle-cells between these, probably homologous with the olfactory cells, they do 

 not reach the surface, nor are they connected with nerve-fibres. Moreover, 

 calcareous concretions are frequent amongst the epithelium cells, so that it is 

 highly probable that the function of the organ in man is entirely in abeyance. In 



Fig. 164. NERVE-FIBRES FROM THE OLFACTORY MUCOUS MEMBRANE. (Max Schultze.) 

 Magnified between 400 and 500 diameters. 



From a branch of the olfactory nerve of the sheep ; at a, a, two dark-bordered or medullated fibres, 

 from the fifth pair, associated with the pale olfactory fibres. 



the embryo, up to eight weeks this epithelium is relatively far better developed, but 

 after this time it appears to undergo retrograde changes. 



Blood-vessels and lymphatics of the nasal fossae. The spheno-palatine 

 branch of the internal maxillary artery enters the cavity by the spheno-palatine 

 foramen and divides into external branches (posterior nasal) to the meatuses and 

 turbinals, sending offsets also to the ethmoidal cells and to the maxillary and frontal 

 sinuses, and an internal branch (naso-palatine, artery of the septum} along the 

 septum to the incisor foramen. The branches of the naso-palatine communicate 

 freely with the anterior and posterior ethmoidal of the ophthalmic. 



The descending palatine branch of the internal maxillary artery gives small offsets 

 to the hinder part of the inferior turbinal and meatus. 



The anterior ethmoidal branch of the ophthalmic artery enters the cavity with 

 the nasal nerve and is distributed to the mucous membrane of the fore part of the 

 septum and outer wall. 



The posterior ethmoidal branch of the same artery sends small twigs to the 

 posterior ethmoidal cells, to the roof, and to the upper part of the septum. 



Lastly a branch from the superior coronary of the facial and the lateral nasal 

 artery supply the part near the anterior nares. The several arteries anastomose 

 freely together in the mucous membrane, and are distributed to three sets of 

 capillaries, viz., a periosteal, glandular, and sub-epithelial. 



