to the lungs, which is done with the aid of fine hairs and _cilia_ in
the nostrils. Persons who breathe through the mouth have at the age
of thirty a gramme of dust in their lungs which they can never get
rid of. Mouth-breathing is a cause of catarrh, of unrefreshing sleep,
of snoring. Moreover, in the words of Dr. T. R. French, "the habit of
breathing through the mouth interferes with general nutrition. The
subjects of this habit are usually anemic, spare and dyspeptic."