d at the same time occasion an increase
of the associate motion of another part, which is catenated with it.

This circumstance nevertheless can only occur in those parts of the system,
whose natural actions are perpetual, and the accumulation of sensorial
power on that account very great, when their activity is much lessened by
the deduction of their usual stimulus; and are therefore only to be found
in the sanguiferous system, or in the alimentary canal, or in the glands
and capillaries. Of the first of which the following is an instance.

The respiration of a reduced atmosphere, that is of air mixed with
hydrogene or azote, quickens the pulse, as observed in the case of Mrs.
Eaton by Dr. Reynolds and Dr. Thornton; to which Dr. Beddoes adds in a
note, that "he never saw an instance in which a lowered atmosphere did not
at the moment quicken the pulse, while it weakened the action of the heart
and arteries." Considerations on Factitious Airs, by Thomas Beddoes and
James Watt, Part III. p. 67. Johnson, London. By the assistance of this new
fact the curious circumstance of the quick production of warmth of the skin
on covering the head under the bed-clothes, which every one must at some
time have experienced, receives a more satisfactory explanation, than that
which is given in Class IV. 1. 1. 2. which was printed before this part of
Dr. Beddoes's Considerations was published.

For if the blood be deprived of its accustomed quantity of oxygen, as in
covering the head in bed, and thus breathing an air rendered impure by
repeated respiration, or by breathing a factitious air with less proportion
of oxygen, which in common respiration passes through the moist membranes
of the lungs, and mixes with the blood, the pulsations of the heart and
arteries become weaker, and consequently quicker, by the defect of the
stimulus of oxygen. And as these vessels are subject to perpetual motion,
the accumulation of the sensorial power of irritation becomes so great by
their lessened activity, that it excites the vessels next connected, the
cutaneous capillaries for instance, into more energetic actions, so as to
produce increased heat of the skin, and greater perspiration.

How exactly this resembles a continued fever with weak and quick pulse!--in
the latter the action of the heart and arteries are lessened by defect of
the excitement of the sensorial power of association, owing to the torpor
or lessened actions of the stomach; hence t