ANATOMICAL DATA. 



1247 



There are two kinds of epithelial cells to be found in the olfactory 

 mucous membrane, as is also the case in many other sensory epithelia, 

 such as the retina, the auditory, and the gustatory. They are, in the first 

 place, the supporting cells, 

 and between them lie the 

 true olfactory cells. Each 

 of the latter is provided with 

 some seven or eight cilium- 

 like processes, 1 which pro- 

 ject from the free surface of 

 the mucous membrane into 

 the serous fluid which mois- 

 tens it. The olfactory cells 

 are prolonged internally into 

 processes which become the 

 fibres of the olfactory nerve. 

 These fibres, which are non- 

 medullated, arborise within 

 the olfactory bulb, within 

 glomeruli formed by these 

 arborisations and the den- 

 drons of the bulb cells. 

 Central processes of the 

 latter carry the olfactory 

 impulses to their centres F IG> 447. 



within the brain. 



The fifth is the nerve of common sensibility to the nose, and in the case of 

 disease or section of this nerve, irritants such as pepper, chlorine, and ammonia 

 produce no irritating effect. When loss of smell likewise occurs, this is 



FIG. 448. Diagram of olfactory path (Cajal). a, the olfactory cells j b, 

 olfactory glomeruli with synapses between their central nerve-pro- 

 cesses and the dendrons of the mitral cells (c) in the olfactory lobe ; 

 d, fibres passing from mitral cells to arborise with dendrons of cells 

 of cerebral cortex, / ; j, collaterals from these fibres ; e, m, other cells 

 in the olfactory lobe ; I, centrifugal fibres derived from cortical cells 

 and terminating in the olfactory lobe. 



probably due to dryness of the mucous membrane, and is thus only indirectly 

 dependent upon division or disease of the nerve. 



Where the olfactory nerves are themselves divided, diseased, or pressed 

 1 von Brunn, loc. cit., S. 638. 



