14. _Hydrops thoracis._ The dropsy of the chest commences with loss of
flesh, cold extremities, pale countenance, high coloured urine in small
quantity, and general debility, like many other dropsies. The patient next
complains of numbness in the arms, especially when elevated, with pain and
difficulty of swallowing, and an absolute impossibility of lying down for a
few minutes, or with sudden starting from sleep, with great difficulty of
breathing and palpitation of his heart.

The numbness of the arms is probably owing more frequently to the increased
action of the pectoral muscles in respiration, whence they are less at
liberty to perform other offices, than to the connexion of nerves mentioned
in Sect. XXIX. 5. 2. The difficulty of swallowing is owing to the
compression of the oesophagus by the lymph in the chest; and the
impossibility of breathing in an horizontal posture originates from this,
that if any parts of the lungs must be rendered useless, the inability of
the extremities of them must be less inconvenient to respiration; since if
the upper parts or larger trunks of the air-vessels should be rendered
useless by the compression of the accumulated lymph, the air could not gain
admittance to the other parts, and the animal must immediately perish.

If the pericardium is the principal seat of the disease, the pulse is quick
and irregular. If only the cavity of the thorax is hydropic, the pulse is
not quick nor irregular.

If one side is more affected than the other, the patient leans most that
way, and has more numbness in that arm.

The hydrops thoracis is distinguished from the anasarca pulmonum, as the
patient in the former cannot lie down half a minute; in the latter the
difficulty of breathing, which occasions him to rise up, comes on more
gradually; as the transition of the lymph in the cellular membranes from
one part to another of it is slower, than that of the effused lymph in the
cavity of the chest.

The hydrops thoracis is often complicated with fits of convulsive
breathing; and then it produces a disease for the time very similar to the
common periodic asthma, which is perhaps owing to a temporary anasarca of
the lungs; or to an impaired venous absorption in them. These exacerbations
of difficult breathing are attended with cold extremities, cold breath,
cold tongue, upright posture with the mouth open, and a desire of cold air,
and a quick, weak, intermittent pulse, and contracted hands.

Th