Remedies which obviate acidity in the stomach, by combining with the
acid, and neutralizing it.
This is the most decided instance of chemical action which occurs in the
history of medicinal operations. We have an acid whose presence excites
morbid symptoms in the _primæ viæ_, and these are immediately removed by
the administration of any one of those substances which are capable of
forming a natural compound with the acid in question, _out of the body_,
and the same proportions are required in both cases for saturation. If a
carbonated alkali be employed, the same disengagement of carbonic acid
takes place in the stomach as would occur in the laboratory, and a new
compound is produced, whose operation varies according to the chemical
nature of the substance employed; thus, the salt which magnesia forms
with the acid in the stomach proves slightly purgative, while that which
lime produces under similar circumstances is distinguished by an
opposite property.