of saliva; which is at the same time more viscid than in its natural state;
because the lymphatics, that open their mouths into the ducts of the
salival glands, and on the membranes, which line the mouth, are likewise
stimulated into stronger action, and absorb the more liquid parts of the
saliva with greater avidity; and the remainder is left both in greater
quantity and more viscid.

The increased absorption in the mouth by some stimulating substances, which
are called astringents, as crab juice, is evident from the instant dryness
produced in the mouth by a small quantity of them.

As the extremities of the glands are of exquisite tenuity, as appears by
their difficulty of injection, it was necessary for them to secrete their
fluids in a very dilute state; and, probably for the purpose of stimulating
them into action, a quantity of neutral salt is likewise secreted or formed
by the gland. This aqueous and saline part of all secreted fluids is again
reabsorbed into the habit. More than half of some secreted fluids is thus
imbibed from the reservoirs, into which they are poured; as in the urinary
bladder much more than half of what is secreted by the kidneys becomes
reabsorbed by the lymphatics, which are thickly dispersed around the neck
of the bladder. This seems to be the purpose of the urinary bladders of
fish, as otherwise such a receptacle for the urine could have been of no
use to an animal immersed in water.

5. The idea of substances disagreeably acrid will also produce a quantity
of saliva in the mouth; as when we smell very putrid vapours, we are
induced to spit out our saliva, as if something disagreeable was actually
upon our palates.

6. When disagreeable food in the stomach produces nausea, a flow of saliva
is excited in the mouth by association; as efforts to vomit are frequently
produced by disagreeable drugs in the mouth by the same kind of
association.

7. A preternatural flow of saliva is likewise sometimes occasioned by a
disease of the voluntary power; for if we think about our saliva, and
determine not to swallow it, or not to spit it out, an exertion is produced
by the will, and more saliva is secreted against our wish; that is, by our
aversion, which bears the same analogy to desire, as pain does to pleasure;
as they are only modifications of the same disposition of the sensorium.
See Class IV. 3. 2. 1.

8. The quantity of saliva may also be increased beyond what is natural, by
the caten