k a
considerable quantity of wine; both contrary to his usual habits of life;
and being obliged to rise early, and to ride a long journey on the next
day; he expected to have found himself weak and soon fatigued; but on the
contrary he performed his journey with unusual ease and alacrity; and
frequently laughed, as he rode, at the wit of the preceding evening. In
both these cases a degree of pain or pleasure actuated the system; and thus
a sensorial power, that of sensation, was superadded to that of irritation,
or volition. See Sect. XXXIV. 2. 6.

2. Similar to this, when the energetic exertions of some parts of the
system in the hot fit of fever arise to a certain excess, a degree of
sensation is produced; as of heat, which particularly increases the actions
of the cutaneous vessels, which are more liable to be excited by this
stimulus. When this additional sensorial power of sensation exists to a
greater degree, the pulse, which was before full, now becomes hard, owing
to the inflammation of the vasa vasorum, or coats of the arteries. In these
cases, whether there is any topical inflammation or not, the fever ceases
to intermit; but nevertheless there are daily remissions and exacerbations
of it; which recur for the most part about six in the evening, when the
solar gravitation is the least, as mentioned in Sect. XXXVI. 3. 7.

3. Thus the introduction of another sensorial power, that of sensation,
converts an intermittent fever into a continued one. If it be attended with
strong pulse, it is termed febris sensitiva irritata, or pyrexia, or
inflammation; if with a weak pulse, it is termed febris sensitiva
inirritata, or typhus gravior, or malignant fever. The seat of the
inflammation is in the glandular or capillary system, as it consists in the
secretion of new fluids, or new fibres, which form new vessels, as they
harden, like the silk of the silk-worm. See Art. 15. of this Supplement.

VI. _Circles of irritative Associate Motions._

1. There are some associate motions, which are perpetually proceeding in
our waking hours, and are catenated by their first link, or in some
subsequent parts of the chain, with the stimuli or the influence of
external things; which we shall here enumerate, as they contribute to the
knowledge of fever. Of these are the irritative ideas, or sensual motions
of the organs of sense, and the muscular motions associated with them;
which, when the chain is disturbed or interrupted, excite the