SMELL. 223 



distributed in its mucous membrane; the lower part is 

 furnished with ciliated epithelium like the rest of the respir- 

 atory tract, as is also the part of the pharynx into which it 

 opens; and in quiet breathing the upper edge of the epiglottis 

 comes almost in contact with the edge of the soft palate 

 which forms its floor behind. When the mouth is shut, the 

 air passes to and from the larynx through the nasal fossae; 

 and, even when the mouth is open, a considerable quantity 

 of. air passes through them; and the current is broken by 

 the various turbinated projections, so that part of it is 

 directed upwards to the olfactory region, and the whole of it 

 is assimilated to the temperature of the body before entering 

 the larynx. In " sniffing," or drawing air into the nose to 

 assist smell, the inspirations are short, abrupt, and repeated, 

 so as to put small quantities of air into rapid motion; and 

 in each inspiration there is a slight but quick contraction of 

 the nostrils, both increasing the rapidity of the air and 

 directing it upwards. 



Both the nasal fossae and the various sinuses opening off 

 from them act as reverberating cavities to improve the 

 timbre of the voice; and it is in connection with the voice, 

 not with smell, that the nasal fossae in the human subject 

 are extensive, They differ from those of quadrupeds in their 

 greater vertical height and diminished extent from before back- 

 wards, and in communicating with larger and more nume- 

 rous sinuses. But, in addition, it will be seen on comparison 

 with any common mammal, such as the dog or the sheep, 

 that in the human subject there is a very small amount of 

 surface provided for the distribution of the olfactory nerves. 

 In those animals the turbinated bones are far more complex, 

 and finer secondary turbinations come off from the main 

 laminae, while all are directed with their ends towards the 

 nostrils, so that the inhaled air is exposed to a most exten- 

 sive sensitive surface. This corresponds with what one 

 would expect, both from the very small comparative size in 

 man of the olfactory bulbs of the brain, and from the ob- 

 viously acute sense of smell in the lower animals, exceeding 

 in some of them, such as the dog, anything which our own 

 senses enable us to conceive. 



164. The olfactory nerves consist each of a brush of fila- 



