Constitutional Peculiarities, or Idiosyncrasies, will sometimes render the operation of the mildest medicine poisonous, “Virum novi,” says Gaubius, “qui cum fatuum lapidum cancrorum pulvisculum ingessit, vix mitius afficitur quam alii ab Arsenico.” I have seen a general Erysipelas follow the application of a blister, and tormina of the bowels, no less severe than those produced by the ingestion of Arsenic, attend the operation of purgatives composed of Senna! In some constitutions Antimony has been known to produce a ptyalism; Dr. James assured Sir George Baker that he knew six instances of it, although the patients thus affected had neither their teeth loosened, nor their breath made offensive. The peculiar susceptibility of certain individuals to the effects of particular plants is also very singular: Murray relates that unpleasant symptoms have been experienced by merely keeping Aconite for some time in the hand, or on the bosom. I am acquainted with two persons in whom the odour of Ipecacuan always produces a most distressing dyspnæa; Mr. Chevalier informs us, that he once knew a lady who could not take Powdered Rhubarb, without an erysipelatous efflorescence almost immediately shewing itself on the skin, and yet she could take it in the form of Infusion with perfect impunity. There are some idiosyncrasies so singular and incredible, that nothing but unimpeachable testimony could sanction our belief in their existence. Schenkius relates a case in which the general law of astringents and cathartics was always reversed. Donatus tells us of a boy whose jaws swelled, whose face broke out in spots, and whose lips frothed, whenever he eat an egg.
The late Pope Pius VII. had such an antipathy to musk, that on one occasion of presentation, an individual of the company having been scented with that perfume, his holiness was obliged to dismiss the party almost immediately.[[289]] Education, and early habits certainly establish very extraordinary peculiarities in different countries with respect to various objects of diet and luxury: what shall we say of the refinement of the Ancients who regarded the flavour of the Citron with disgust, while the odour of putrid fish was deemed by them so exquisite, that they carried it about in caskets of onyx as a favourite perfume! Custom makes the Greenlander relish his train oil; and Dr. Heberden tells us, that there is a town in North America, where the spring-water is brackish, and that, when the inhabitants visit any other province, they choose to put salt into their tea or punch, in order, as they say, “to make it taste as it should do.”[[290]]
Climate. Several observations have already been offered upon the influence of Climate in affecting the activity of our remedies.[[291]] With regard to its relations to Dose, I have only one remark to make to the English practitioner, and that by the way of caution, that he will not allow his own previous experience in hot climates, or the persuasions of other tropical practitioners to induce him to administer such doses of Mercury, in England, as may have been found salutary in India, or in other Colonies of similar temperature.
The popular scheme of Gaubius for graduating the doses of medicine to different ages, which was published in several of the former editions of this work, is now omitted, as being less easy of application than the following simple formula by Dr. Young.
RULE.
For children under twelve years, the doses of most Medicines must be diminished in the proportion of the Age, to the Age increased by 12.
| thus at two years to ⅐—viz. | ||
| 2 | 1 | |
| = | ||
| 2 + 12 | 7 | |
| At 21 the full dose may be given. | ||
Every general rule however respecting the doses of medicines will have exceptions. Thus children will bear larger doses of Calomel than even adults, and many medicines which do not affect adults, although exhibited in considerable quantities, prove injurious even in small doses to children.[[292]]
In concluding this part of the subject, it is proper to impress upon the practitioner the importance of writing his prescriptions in legible characters, and of avoiding all those abbreviations which are not generally understood, or which are capable of misconstruction.[[293]]
On the Particular Forms of Remedies, and the general principles upon which their construction and administration are to be regulated.