qua non, as an influence,
which penetrating the mass, removes the particles of it to a greater
distance from each other, so as to allow their movement over each other, in
the same manner as heat is conceived to produce the fluidity of water; not
by stimulus, but by its penetrating influence? Or may elementary heat in
its uncombined state be supposed to act only as an influence necessary to
life in its natural quantity; whence torpor and death follows the eduction
of it from the body; but in its increased state above what is natural, or
usual, that it acts as a stimulus; which we have a sense to perceive; and
which excites many parts of the system into unnatural action? See Class IV.
1. 1. C.

2. _Vita hiemi-dormientium._ The torpor of insects, and birds, and
quadrupeds, during the cold season, has been called sleep; but I suppose it
must differ very much from that state of animal life, since not only all
voluntary power is suspended, but sensation and vascular motion has ceased,
and can only be restored by the influence of heat. There have been related
instances of snails, which have recovered life and motion on being put into
water after having experienced many years of torpidity, or apparent death,
in the cabinets of the curious. Here the water as well as the heat are
required not only as a stimulus, but as a causa sine qua non of fluidity
and motion, and consequent life.

3. _Pullulatio arborum._ The annual revivescence of the buds of trees seems
not only to be owing to the influence of the returning warmth of the
spring, but also to be catenated with solar gravitation; because seeds and
roots and buds, which are analogous to the eggs of animals, put forth their
shoots by a less quantity of heat in spring, than they had undergone in the
latter part of autumn, which may however be ascribed to their previous
torpid state, and consequent accumulation of sensorial power, or
irritability; as explained in Botanic Garden, Part II. Cant. I. l. 322.
note. Other circumstances, which countenance the idea, that vegetation is
affected by solar gravitation, as well as by heat, may be observed in the
ripening of the seeds of plants both in those countries where the summers
are short, and in those where they are long. And by some flowers closing
their bells at noon, or soon after; and hence seem to sleep rather at solar
diurnal periods, than from the influence of cold, or the deficiency of
light.

4. _Orgasmatis venerei periodus.