he power we have of comparing the present perceptions of one
sense with those of another, as explained in Sect. XIV. 2. 5. And also by
comparing the tribes of ideas, which the symbols of pictures, or of
languages, suggest to us, by intuitive analogy with our previous
experience, that is, with the common course of nature. See Class III. 2. 2.
3. on Credulity.

ADDITION VI.

_Please to add the following in page 14, after line 20._

_Cold and hot Fit._

As the torpor, with which a fit of fever commences, is sometimes owing to
defect of stimulus, as in going into the cold-bath; and sometimes to a
previous exhaustion of the sensorial power by the action of some violent
stimulus, as after coming out of a hot room into cold air; a longer time
must elapse, before there can be a sufficient accumulation of sensorial
power to produce a hot fit in one case than in the other. Because in the
latter case the quantity of sensorial power previously expended must be
supplied, before an accumulation can begin.

The cold paroxysm commences, when the torpor of a part becomes so great,
and its motions in consequence so slow or feeble, as not to excite the
sensorial power of association; which in health contributes to move the
rest of the system, which is catenated with it. And the hot fit commences
by the accumulation of the sensorial power of irritation of the part first
affected, either so as to counteract its deficient stimulus, or its
previous waste of sensorial power; and it becomes general by the
accumulation of the sensorial power of association; which is excited by the
renovated actions of the part first affected; or becomes so great as to
overbalance the deficient excitement of it. On all these accounts the hot
fit cannot be supposed to bear any proportion to the cold one in length of
time, though the latter may be the consequence of the former. See Suppl. I.
16. 8.

ADDITION VII. ON WARMTH.

_To be added at the end of the Species Sudor Calidus, in Class I. 1. 2. 3._

When the heat of the body in weak patients in fevers is increased by the
stimulus of the points of flannel, a greater consequent debility succeeds,
than when it is produced by the warmth of fire; as in the former the heat
is in part owing to the increased activity of the skin, and consequent
expenditure of sensorial power; whereas in the latter case it is in part
owing to the influx of the fluid matter of heat.

So the warmth produced by equitation, or by rub