ove through a much less area at
each pulsation, whether these motions are occasioned by defect of their
natural stimuli, or by the defect of other irritative motions with which
they are associated, or from the inirritability of the arterial system,
that is, from a decreased quantity of sensorial power, another kind of
fever arises; which may be termed, Typhus irritativus, or Febris irritativa
pulsu debili, or irritative fever with weak pulse. The former of these
fevers is the synocha of nosologists, and the latter the typhus mitior, or
nervous fever. In the former there appears to be an increase of sensorial
power, in the latter a deficiency of it; which is shewn to be the immediate
cause of strength and weakness, as defined in Sect. XII. 1. 3.

It should be added, that a temporary quantity of strength or debility may
be induced by the defect or excess of stimulus above what is natural; and
that in the same fever _debility always exists during the cold fit, though
strength does not always exist during the hot fit._

These fevers are always connected with, and generally induced by, the
disordered irritative motions of the organs of sense, or of the intestinal
canal, or of the glandular system, or of the absorbent system; and hence
are always complicated with some or many of these disordered motions, which
are termed the symptoms of the fever, and which compose the great variety
in these diseases.

The irritative fevers both with strong and with weak pulse, as well as the
sensitive fevers with strong and with weak pulse, which are to be described
in the next section, are liable to periodical remissions, and then they
take the name of intermittent fevers, and are distinguished by the
periodical times of their access.

II. For the better illustration of the phenomena of irritative fevers we
must refer the reader to the circumstances of irritation explained in Sect.
XII. and shall commence this intricate subject by speaking of the quick
pulse, and proceed by considering many of the causes, which either
separately or in combination most frequently produce the cold fits of
fevers.

1. If the arteries are dilated but to half their usual diameters, though
they contract twice as frequently in a given time, they will circulate only
half their usual quantity of blood: for as they are cylinders, the blood
which they contain must be as the squares of their diameters. Hence when
the pulse becomes quicker and smaller in the same pr