THE OLFACTORY NERVES. 383 



sebaceous glands of the skin, and covered with cylindrical or columnar 

 epithelial cells, having flattened ends, but being destitute of cilia. 

 Between the cells of this epithelium, are found other, finer, spindle- 

 shaped columns, or rods, which are of a varicose shape, and project 

 beyond the surface; they are named the olfactory^ cells. (Schultz.) 

 Lastly, the various sinuses connected with the nasal fossae, are lined 

 by a thin, red, smooth, ciliated mucous membrane. The lining mem- 

 brane of the lower region next to the nostrils, is usually dry ; whilst 

 that of the other two regions, and of the sinuses, is constantly moist, 

 either with simple mucus, or with the special secretion of the small 

 glands in the upper region. The lower region is also the thinnest, 

 and least vascular; the sinuses are much more so; whilst the upper 

 and middle regions are thicker and more vascular, especially over the 

 turbinated bones. 



The nerves supplying the nasal mucous membrane are derived from 

 three sources. First, from the nasal and anterior dental branches of 

 the fifth pair of cranial nerves, which are distributed to all its parts ; 

 secondly, from the vidian, naso-palatine, descending palatine, and sphe- 

 no-palatine branches of the sympathetic nerve, which also probably 

 have a general distribution ; thirdly, there are the terminal branches 

 of the first pair of cranial nerves, or olfactory nerves, Fig. 73, 2. The 



Fig. 73. 



Fig. 73. Vertical section through the right nasal fossa, showing the outer side of that fossa, with a part of 

 the base of the cranium, the palate, and the nose. 1, the olfactory tract ending anteriorly in the olfactory 

 lobe, or bulb, resting on the cribriform plate of the ethmoid bone. 2, superior turbinated portion of the 

 ethmoid bone, corresponding with the upper part of the olfactory region, and covered with the network of 

 the branches of the olfactory nerves. 3, middle turbinated portion of the ethmoid bone, covered with a 

 few olfactory nerves, and also forming part of the olfactory region. 4> lower turbinated bone, receiving 

 only branches of the fifth nerve, 5, which also supplies the palate. The anterior region of the nasal fossa 

 receives branches also derived from the fifth nerve. (After Arnold.) 



latter proceed from the olfactory lobes, 1, within the cranium, and pass 

 through the small openings in the sieve-like plates of the ethmoid bone, 

 to gain the upper part or roof of the nasal fossae. They are about 

 twenty in number, are arranged in each fossa in three groups, one of 

 which supplies the roof, another distributed on the surface of the cel- 

 lular part of the ethmoid bone, 2, 3, as low down as the middle turbi- 

 nated bone, whilst an inner group spreads out on the upper third of 

 the nasal septum. The branches of these nerves everywhere form a 



