as cod-liver oil may give rise to disagreeable eruptions.
Christison speaks of a boy ten years old who was said to have been
killed by the ingestion of two ounces of Epsom salts without inducing
purgation; yet this common purge is universally used without the
slightest fear or caution. On the other hand, the extreme tolerance
exhibited by certain individuals to certain drugs offers a new phase of
this subject. There are well-authenticated cases on record in which
death has been caused in children by the ingestion of a small fraction
of a grain of opium. While exhibiting especial tolerance from peculiar
disposition and long habit, Thomas De Quincey, the celebrated English
litterateur, makes a statement in his "Confessions" that with impunity
he took as much as 320 grains of opium a day, and was accustomed at one
period of his life to call every day for "a glass of laudanum negus,
warm, and without sugar," to use his own expression, after the manner a
toper would call for a "hot-Scotch."

The individuality noted in the assimilation and the ingestion of drugs
is functional as well as anatomic. Numerous cases have been seen by all
physicians. The severe toxic symptoms from a whiff of cocain-spray, the
acute distress from the tenth of a grain of morphin, the gastric crises
and profuse urticarial eruptions following a single dose of
quinin,--all are proofs of it. The "personal equation" is one of the
most important factors in therapeutics, reminding us of the old rule,
"Treat the patient, not the disease."

The idiosyncrasy may be either temporary or permanent, and there are
many conditions that influence it. The time and place of
administration; the degree of pathologic lesion in the subject; the
difference in the physiologic capability of individual organs of
similar nature in the same body; the degree of human vitality
influencing absorption and resistance; the peculiar epochs of life; the
element of habituation, and the grade and strength of the drug,
influencing its virtue,--all have an important bearing on untoward
action and tolerance of poisons.

It is not in the province of this work to discuss at length the
explanations offered for these individual idiosyncrasies. Many authors
have done so, and Lewin has devoted a whole volume to this subject, of
which, fortunately, an English translation has been made by Mulheron,
and to these the interested reader is referred for further information.
In the following lines exa