Another method of inducing sleep is delivered in a very ingenious work
lately published by Dr. Beddoes. Who, after lamenting that opium frequently
occasions restlessness, thinks, "that in most cases it would be better to
induce sleep by the abstraction of stimuli, than by exhausting the
excitability;" and adds, "upon this principle we could not have a better
soporific than an atmosphere with a diminished proportion of oxygene air,
and that common air might be admitted after the patient was asleep."
(Observ. on Calculus, &c. by Dr. Beddoes, Murray.) If it should be found to
be true, that the excitability of the system depends on the quantity of
oxygene absorbed by the lungs in respiration according to the theory of Dr.
Beddoes, and of M. Girtanner, this idea of sleeping in an atmosphere with
less oxygene in its composition might be of great service in epileptic
cases, and in cramp, and even in fits of the asthma, where their periods
commence from the increase of irritability during sleep.

Sleep is likewise said to be induced by mechanic pressure on the brain in
the cases of spina bifida. Where there has been a defect of one of the
vertebræ of the back, a tumour is protruded in consequence; and, whenever
this tumour has been compressed by the hand, sleep is said to be induced,
because the whole of the brain both within the head and spine becomes
compressed by the retrocession of the fluid within the tumour. But by what
means a compression of the brain induces sleep has not been explained, but
probably by diminishing the secretion of sensorial power, and then the
voluntary motions become suspended previously to the irritative ones, as
occurs in most dying persons.

Another way of procuring sleep mechanically was related to me by Mr.
Brindley, the famous canal engineer, who was brought up to the business of
a mill-wright; he told me, that he had more than once seen the experiment
of a man extending himself across the large stone of a corn-mill, and that