THE SENSE OF SMELL. 621 
thelium of the olfactory region are found peculiar hair-cells 
highly suggestive of those of the labyrinth of the ear, and 
Fic. 463.—Parts concerned in smell (after Hirschfeld). 
1, olfactory ganglion and nerves; 2, 
branch of nasal nerve, distributed over the turbinated bones. 
which are to be regarded as the end-organs of smell. If aro- 
matic bodies be held before the nose, and respiration suspended, 
they will not be recognized as such, 
and it is well known that sniffing 
greatly assists the sense of smell. 
Again, if fluids, such as eaw de Co- 
logne, be held in the nose, their aroma 
is not detected ; and immediately after 
water has been kept in the nostrils 
for a few seconds, it may be noticed 
that smell is greatly blunted. Such 
is the case also when the mucous 
membrane is much swollen from a 
cold. There can be no doubt that the 
presence of fluid in the above cases is 
injurious to the delicate hair-cells, 
and that smell is dependent upon the 
excitation of these cells by eatremely 
minute particles emanating from aro- 
matic bodies. 
When ammonia is held before the 
nose, a powerful sensation is experi- 
Fig. 464.—End-organs concerned in 
smell (after K6lliker). 1, from 
frog—a, epithelial cell of the ol- 
factory area; b, olfactory cell. 
2, small branch of olfactory 
nerve of frog, breaking up into 
a brush of varicose fibers. 3, 
olfactory cell of sheep. 
enced; but this is not smell proper, but an affection of ordi- 
nary sensation, owing to stimulation of the terminals of the 
