, whom I saw yesterday, was seized with asthma on the
retrocession, or ceasing of eruptions on his face.

The convulsive asthma, as well as the hydropic, are more liable to return
in hot weather; which may be occasioned by the less quantity of oxygen
existing in a given quantity of warm air, than of cold, which can be taken
into the lungs at one inspiration. They are both most liable to occur after
the first sleep, which is therefore a general criterion of asthma. The
cause of this is explained in Sect. XVIII. 15. and applies to both of them,
as our sensibility to internal uneasy sensation increases during sleep.

When children are gaining teeth, long before they appear, the pain of the
gums often induces convulsions. This pain is relieved in some by sobbing
and screaming; but in others a laborious respiration is exerted to relieve
the pain; and this constitutes the true asthma convulsivum. In other
children again general convulsions, or epileptic paroxysms, are induced for
this purpose; which, like other epilepsies, become established by habit,
and recur before the irritation has time to produce the painful sensation,
which originally caused them.

The asthma convulsivum is also sometimes induced by worms, or by acidity in
the stomachs of children, and by other painful sensations in adults; in
whom it is generally called nervous asthma, and is often joined with other
epileptic symptoms.

This asthma is distinguished from the peripneumony, and from the croup, by
the presence of fever in the two latter. It is distinguished from the
humoral asthma, as in that the patients are more liable to run to the cold
air for relief, are more subject to cold extremities, and experience the
returns of it more frequently after their first sleep. It is distinguished
from the hydrops thoracis, as that has no intervals, and the patient sits
constantly upright, and the breath is colder; and, where the pericardium is
affected, the pulse is quick and unequal. See Hydrops Thoracis, I. 2. 3.
14.

M. M. Venesection once. A cathartic with calomel once. Opium. Assafoetida.
Warm bath. If the cause can be detected, as in toothing or worms, it should
be removed. As this species of asthma is so liable to recur during sleep,
like epileptic fits, as mentioned in Section XVIII. 15. there was reason to
believe, that the respiration of an atmosphere mixed with hydrogen, or any
other innocuous air, which might dilute the oxygen, would be useful in
prev