If more attention were given by prescribers to the possibilities of ambiguous nomenclature, it would be a great boon to pharmacists and would save much worry and occasional maltreatment. For preparations mentioned in the British Pharmacopoeia the name there found should be used, and in ordering those not included in the B.P. the initials of the Pharmacopoeia or the name of the standard work in which the formula may be found should be given.

No hard-and-fast rule can be laid down for the dispenser's guidance when he finds an article mentioned by a name which applies to two or more preparations. Probably the date of the prescription may help him. Suppose the following prescription is presented:

The only official simple tincture existing when that prescription was written was tinctura cinchona flavae. This tincture was expunged from the 1898 Pharmacopoeia and a tincture of the red bark took its place, but there is no law which compels the dispenser to give the latter tincture in such an instance as the above. The patient has used the old tincture and may prefer it. The introduction of a new Pharmacopoeia raises many questions of this kind in the case of preparations which have been altered. It is obligatory upon dispensing chemists to use the preparations of the British Pharmacopoeia, 1914, after January 1, 1915, for prescriptions written after 1914, but not for prescriptions written before 1915. The following prescription is a good example of a case in which the substitution of an altered preparation for an old one gives quite a different result:

The liquor bismuthi of the 1867 B.P. gave a clear mixture, because it contained excess of ammonium citrate and nitrate which prevented precipitation of bismuth carbonate. The present liquor does not contain the excess, so the mixture made with it has a copious precipitate.

Sir W. Whitla says the dispenser will often be at a loss to understand the meaning of the prescriber when he orders some preparations out of their official names. Then he must either have a consultation with the prescriber or rely upon his experience. Sir William gives the following examples: When 'magnes. calc.' is ordered, magnesia B.P. should be used; when 'magnes. carb.'the heavy preparation is usually intended; when 'bismuth' or ' bismuth, alb.' is prescribed, the subnitrate is the preparation generally in the mind of the physician; when 'aqua menth.' is ordered, 'aq. menth. pip. should not be used, but aq. menth. sativ. is the intention of the prescriber.'

This is a good example of the difference of opinion amongst authorities. In some establishments aq. menthae virid. is always dispensed for 'aq. menthae,' but this custom is not general. Aq. menth. virid. is ordered only by old practitioners, but aq. menth. pip. is decidedly the favourite, and is used officially as a flavouring agent. For these reasons it is advisable to use aq. menth. pip. when 'aq. menth.' is ordered, unless the dispenser knows the intention of the prescriber to be the contrary. In 1888 The Chemist and Druggist obtained the opinions of thirty leading London consultants on the question, 'What is aqua menthae?' and only two or three said, 'Aq. menthae vir.'

Sir William Whitla's remarks regarding magnesia recall a comment made in a previous edition. It was then said that some apparent difficulties can be settled by reference to the Pharmacopoeia- e.g., magnesia, prescribed as such, means the mag. calc. pond, according to the B.P. The light variety is expressly designated magnesia levis. This no longer strictly applies, for the term 'magnesia' has been changed to 'magnesia ponderosa,'and'ponderosa' has also been added to magnesii carbonas. A conventional understanding exists among dispensers, when 'magnesia' and 'magnesii carbonas' are prescribed without their specific designation of 'levis' or 'ponderosa,' that the light should be used in mixtures and the heavy in powders. The light makes a smooth mixture and remains well in suspension ; the heavy retains the minimum of bulk in powders-a distinct advantage when for children.

Certain alterations in nomenclature and potency of well-known articles and preparations are made by the British Pharmacopoeia, 1914, which are specified on pages xxv and xxvi of the book. Dispensers should bear these in mind when compounding prescriptions dated anterior to January 1, 1915. The more important of these and other ambiguities are here noted:

Acetum scillae, B.P. 1914, is twice the strength of the 1898 preparation, but syr. scillae is approximately as before.

Acid, nitro-hydrochlor., prescribed without the addition of the qualifying term 'dil.,' is an instance of careless prescribing, but it can hardly occasion a doubt, as the strong compound acid is not official dither, chlor., formerly a source of some doubt, is now represented in the British Pharmacopoeia by spirit of chloroform, the synonyms of which are chloric ether and spirit of chloric ether. It may here be pointed out that the original preparation made by Messrs. Duncan, Flockhart & Co. is distilled, is not of the same chloroform strength as the official spirit, and is soluble in water. Some prescribers still prefer it.