names of diseases is, that one name
frequently includes more than one disease, either existing at the same time
or in succession. Thus the pain of the bowels from worms is caused by the
increased action of the membrane from the stimulus of those animals; but
the convulsions, which sometimes succeed these pains in children, are
caused by the consequent volition, and belong to another class.

To discover under what class any disease should be arranged, we must first
investigate the proximate cause; thus the pain of the tooth-ach is not the
cause of any diseased motions, but the effect; the tooth-ach therefore does
not belong to the class of Sensation. As the pain is caused by increased or
decreased action of the membranes of the tooth, and these actions are owing
to the increase or decrease of irritation, the disease is to be placed in
the class of irritation.

To discover the order it must be inquired, whether the pain be owing to
increased or defective motion of the pained membrane; which is known by the
concomitant heat or coldness of the part. In tooth-ach without inflammation
there is generally a coldness attends the cheek in its vicinity; as may be
perceived by the hand of the patient himself, compared with the opposite
cheek. Hence odontalgia is found to belong to the order of decreased
irritation. The genus and species must be found by inspecting the synopsis
of the second order of the class of Irritation. See Class I. 2. 4. 12.

This may be further elucidated by considering the natural operation of
parturition; the pain is occasioned by the increased action or distention
of the vessels of the uterus, in consequence of the stimulus of the fetus;
and is therefore caused by increased irritation; but the action of the
abdominal muscles in its exclusion are caused by the pain, and belong to
the class of increased sensation. See Class II. 1. 1. 12. Hence the
difficulty of determining, under what class of diseases parturition should
be arranged, consists in there being two kinds of diseased actions
comprehended under one word; which have each their different proximate
cause.

In Sect. XXXIX. 8. 4. and in Class II. 1. 1. 1. we have endeavoured to give
names to four links of animal causation, which conveniently apply to the
classification of diseases; thus in common nictitation, or winking with the
eyes without our attention to it, the increased irritation is the proximate
cause; the stimulus of the air on the dry corne