It is cultivated on the large scale in England, France, Germany, and North America.

History-Mentha piperita was first observed in Hertfordshire by Dr. Eales and communicated to Ray, who in the second edition of his Synopsis Stirpium Britannicarum, 1696, noticed it under the name of Mentha spicis brevioribus et habitioribus, foliis Mentha fusca, sapore fervido piperis; and in his Historia Plantarum1 as "Mentha palustris Peper-Mint." 2 Dale who found the plant in the adjoining county of Essex, states that it is esteemed a specific in renal and vesical calculus; and Ray in the third edition of his Synopsis, declares it superior to all other mints as a remedy for weakness of the stomach and for diarrhoea. Peppermint was admitted to the London Pharmacopoeia in 1721, under the designation of Mentha piperitis sapore.

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The cultivation of peppermint at Mitcham in Surrey, dates from about 1750, at which period only a few acres of ground were there devoted to medicinal plants. At the end of the last century, above 100 acres were cropped with peppermint. But so late as 1805 there were no stills at Mitcham, and the herb had to be carried to London for the extraction of the oil. Of late years the cultivation has diminished in extent, by reason of the increased value of land and the competition of foreign oil of peppermint.

In Germany, peppermint became practically known in the latter half of the last century, especially through the recommendation of Knigge.5

out runners.

Description-The rootstock of peppermint is perennial, throwing The stem is erect, 3 to 4 feet high, when luxuriant somewhat branched below with erecto-patent branches, firm, quadrangular, slightly hairy, often tinged with purple. Leaves all stalked, the stalks of the lower to of an inch long, naked or nearly so, the leaf lanceolate, narrowed or rather rounded towards the base, the point narrowed out and acute, the lowest 2 to 3 inches long by about of an inch broad, naked and dull green above, paler and glandular all over, but only slightly hairy upon the veins beneath; the teeth sharp, fine, and erecto-patent. Inflorescence in a loose lanceolate or acutely conical spike, 2 to 3 inches long by about of an inch broad at the base, the lowest whorls separate, and usually the lowest bracts leaf-like. Bracteoles lanceolate acuminate, about equalling the expanded flowers, slightly ciliated. Pedicels 1 to 1 lines long, purplish, glandular but not hairy. Calyx often purplish, the tube about 1 line long and the teeth a line, the tube campanulate-cylindrical, purplish, not hairy, but dotted over with prominent glands; the teeth lanceolate subulate, furnished with short erecto-patent hairs. Corolla reddish purple about twice as long as the calyx, naked both within and without. Nut smooth (rugose, according to our observation). The odour and taste are strongly aromatic.

1 Tomus iii. (1704) 284.

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* I have examined the original specimen still preserved among Ray's plants in the British Museum and find it to agree perfectly with the plant now in cultivation.D. H.

Pharmacologia Supplementum, Lond. 1705. 117.

In var. 2. vulgaris of Sole, M. piperita B. Smith, the plant is more hairy, with the spikes broader and shorter, or even bluntly capitate.

Chemical Composition-The constituent for the sake of which peppermint is cultivated, is the essential oil, Oleum Mentha piperita, a colourless, pale yellow, or greenish liquid, of sp. gr. varying from 0·84 to 0.92. It has a strong and agreeable odour, with a powerful aromatic taste, followed by a sensation of cold when air is drawn into the mouth. We find that the Mitcham oil examined by polarized light in a column 50 mm. long, deviates 14-2° to the left.

When oil of peppermint is cooled to -4° C., it sometimes deposits colourless hexagonal crystals of Peppermint Camphor, C10H18 + H2O, called also Menthol. This camphor (the deposit of which in the oil we have not observed) boils at 210° C. and possesses the odour of the crude oil; it deviates the ray of polarized light to the left. The proportion of menthol contained in oils of different origin is very variable. Pure crystallized menthol is sometimes found in commerce under the name of Chinese Oil of Peppermint.1

The liquid part of the oil of peppermint has not yet been chemically investigated.

Oil of peppermint is not uniform in constitution, nor in its flavour and chemical behaviour. Accurate means of ascertaining its value and purity are wanting.

If 50 to 70 drops of peppermint oil are shaken with one drop of nitric acid, sp. gr. about 1-2, the mixture changes from faintly yellowish to brownish and, after an hour or two, exhibits a bluish, violet or greenish colour; in reflected light, it appears reddish and not transparent. The colour thus produced lasts a fortnight. We have thus examined the various samples of peppermint oil at our command, and may state that the finest among them assume the most beautiful coloration and fluorescence, which however shows very appreciable differences. An inferior oil of American origin was not coloured; and a very old sample of an originally excellent English oil was likewise not coloured by the test. Menthol, that is to say the Chinese oil of peppermint, is not altered when similarly treated. The nitric acid test is not capable of revealing adulterations of peppermint oil, for the coloration takes place with an oil, to which a considerable quantity of oil of turpentine has been added.

Remarkable colorations of a different hue are also displayed by the various kinds of oil of peppermint if other chemical agents are mixed with it. Thus green or brownish tints are produced by means of anhydrous chloral; the oil becomes bluish or greenish or rose-coloured if shaken with a concentrated solution of bisulphite of sodium. It is worthy of note that oils of different origin, which cannot be distinguished by means of nitric acid, exhibit totally different colorations if mixed with either of the liquids just named. This behaviour may be of some use in the examination of commercial sorts of peppermint oil.

As to bisulphite of sodium, it yields a solid compound with certain kinds of peppermint oil, which we have not yet examined.

It is distilled at Canton from a plant which appears to be Mentha arvensis L. var. Javanica (M. Javanica Bl.) The oil was exported from Canton in 1872, to the extent

of 800 b.; it was valued at about 30s. per b.-See also Flückiger in Pharm. Journ. Oct. 14, 1871. 321.

2 Pharm. Journ. Feb. 25, 1871. 682.

Production and Commerce-In several parts of Europe as well as in the United States, peppermint is cultivated on the large scale as a medicinal plant.

In England the culture is carried on in the neighbourhood of Mitcham in Surrey, near Wisbeach in Cambridgeshire, Market Deeping in Lincolnshire, and Hitchin in Hertfordshire.

At Mitcham in 1850, there were about 500 acres under cultivation; in 1864 only about 219 acres.1 At Market Deeping there were in 1871 about 150 acres cropped with peppermint. The usual produce in oil may be reckoned at 8 to 12 lb. per acre. The fields of peppermint at Mitcham are level, with a rich, friable soil, well manured and naturally retentive of moisture. The ground is kept free from weeds, and in other respects. is carefully tilled. The crop is cut in August, and the herb is usually allowed to dry on the ground before it is consigned to the stills. These are of large size, holding 1000 to 2000 gallons, and heated by coal; each still is furnished with a condensing worm of the usual character, which passes out into a small iron cage secured by a padlock, in which stands the oil separator. The distillation is conducted at the lowest possible temperature. The water that comes over with the oil is not distilled with another lot of herb, but is for the most part allowed to run away, a very little only being reserved as a perquisite of the workmen. The produce is very variable, and no facilities exist for estimating it with accuracy.2 It is however stated that a ton of dried peppermint yields from 2 to 3 pounds of oil, which equals 011 to 0.15 per cent. But we have been assured by a grower at Mitcham that the yield is as much as 6 pounds from a ton, or 0.26 per cent.

At Mitcham and its neighbourhood, two varieties of peppermint are at present recognized, the one being known as White Mint, the other as Black Mint, but the differences between the two are very slight. The Black Mint has purple stems; the White Mint, green stems, and as we have observed, leaves rather more coarsely serrated than those of the Black. The Black Mint is more prolific in essential oil than the White, and hence more generally cultivated; but the oil of the latter is superior in delicacy of odour and commands a higher price. White Mint is said to be principally grown for drying in bundles, or as it is termed "bunching."

Peppermint is grown on a vastly larger scale in America, the localities where the cultivation is carried on being Southern Michigan, Western New York, and Ohio. In Michigan where the plant was introduced in 1835, there were in 1858 about 2100 acres devoted to its growth, all with the exception of about 100 acres being in the county of St. Joseph. The average produce of this district was estimated in 1858, at 15,000 b; but the yield fluctuates enormously, and in the exceptionally fine season of 1855, it was reckoned at 30,000 b. We must suppose that it is now much larger, for we have been informed by Mr. H. G. Hotchkiss, of Lyons, Wayne County, State of New York, one of the most wellknown distillers, in a letter under date Oct. 10, 1871, that the quantity

1 Pharm. Journ. x. (1851) 297. 340; also Warren in Pharm. Journ. vi. (1865) 257. To these papers and to personal inquiries we are indebted for most of the particulars relating to peppermint culture at Mitcham.

Only the larger growers have stills.

These they let to smaller cultivators who pay so much for distilling a charge, i.e. whatever the still can be made to contain, without reference to weight. Hence the dried herb is preferred to the fresh, as a larger quantity can be distilled at one time.

sent out by him in the previous year, reached the enormous amount of 57,365 b. From the statistics quoted by Stearns1 it would appear that the produce of oil per acre is somewhat higher than in England, but from various causes, information on this head cannot be very reliable.

Peppermint is cultivated at Sens in the department of the Yonne in France and in Saxony, and very recently it has been tried in the Neilgherry Hills in Southern India.

Peppermint oil varies greatly in commercial value, that of Mitcham commanding twice or three times as high a price as the finest American. Even the oil of Mitcham is by no means uniform in quality, certain plots of ground affording a product of superior fragrance. A damp situation or badly drained ground, is well known to be unfavourable both to the quantity and quality of oil.

The presence of weeds among the peppermint is an important cause of deterioration to the oil, and at Mitcham some growers give a gratuity to their labourers to induce them to be careful in throwing out other plants when cutting the herb for distillation. One grower of peppermint known to us was compelled to abandon the cultivation, owing to the enormous increase of Mentha arvensis L. which could not be separated, and which when distilled with the peppermint ruined the flavour of the latter. In America great detriment is occasioned by the growth of Erigeron Canadense L. Newly cleared ground planted with peppermint, is liable to the intrusion of another plant of the order Compositæ, Erechtites hieracifolia Raf., which is also highly injurious to the quality of the oil.3

Uses-A watery or spirituous solution of oil of peppermint is a grateful stimulant, and is a frequent adjunct to other medicines. Oil of peppermint is extensively consumed for flavouring sweetmeats and cordials.

HERBA PULEGII.

Pennyroyal; F. Menthe pouliot, Pouliot vulgaire; G. Polei.

Botanical Origin-Mentha Pulegium L., a small perennial aromatic plant, common throughout the south of Europe and extending northward to Sweden, Denmark, England and Ireland, eastward to Asia Minor and Persia, and southward to Abyssinia, Algeria, Madeira and Teneriffe. It has been introduced into North 5 and South America. For medicinal use it is cultivated on a small scale.

History-Pennyroyal was in high repute among the ancients. Both Dioscorides and Pliny describe its numerous virtues. In Northern Europe it was also much esteemed, as may be inferred from the frequent reference to it in the Anglo-Saxon works on medicine.

1 To whose paper On the Peppermint Plantations of Michigan in the Proceedings of the Americ. Pharm. Assocn. for 1858, we owe the few particulars for which we can here afford space.

Journ. de Pharm. viii. (1868) 130.Abstract from Roze, La Menthe poivrée, sa culture en France, ses produits, falsifications de l'essence et moyens de les reconnaître, Paris 1868. 43 pages.

Maisch, American Journ. of Pharm., March 1870. 120.

4 Pennyroyal, in old herbals Puliol royal, is derived from Puleium regium, an old Latin name given from the supposed efficacy of the plant in destroying fleas (Prior).

5 The native Pennyroyal is however a different plant, namely Hedeoma pulegioides Pers.

Gerarde considered the plant to be "so exceedingly well known to all our English nation" that it needed no description. In his time (circa 1590), it used to be collected on the commons round London, whence it was brought in plenty to the London markets. At the present day pennyroyal has fallen into neglect, and is not named in the British Pharmacopoeia of 1867.

Description-The plant has a low, decumbent, branching stem, which in flowering rises to a height of about 6 inches. Its leaves, scarcely an inch in length and often much less, are petiolate, ovate, blunt, crenate at the margin, dotted with oil-glands above and below. The flowers are arranged in a series of dense, globose whorls, extending for a considerable distance up the stem. The whole plant is more or less hairy. It has a strong fragrant odour, less agreeable to most persons than that of peppermint or spearmint. Its taste, well perceived in the distilled water, is highly aromatic.

Chemical Composition-The most important constituent of pennyroyal is the essential oil, known in pharmacy as Oleum Pulegii, to which is due the odour of the plant. It has been examined by Kane,1 according to whom it has a sp. gr. of 0.927. Its boiling was found to fluctuate between 183° and 188° C. The formula assigned to it by this chemist is C10H160.

Production-Pennyroyal is cultivated at Mitcham and is mostly sold dried; occasionally the herb is distilled for essential oil. The oil found in commerce is however chiefly French or German, and far less costly than that produced in England.

Uses-The distilled water of pennyroyal is carminative and antispasmodic, and is used in the same manner as peppermint water.

HERBA THYMI VULGARIS.

Garden Thyme; F. Thym vulgaire; G. Thymiankraut.

Botanical Origin-Thymus vulgaris L., a small, erect, woody shrub reaching 8 to 10 inches in height, gregarious on sterile uncultivated ground in Portugal, Spain, Southern France and Italy, and in the mountainous parts of Greece. On Mont Ventoux near Avignon, it reaches an elevation above the sea of 3700 ft. (Martins). It is commonly cultivated in English kitchen gardens as a sweet herb.2

History Garden thyme was commonly cultivated in England in the 16th century, and was well figured and described by Gerarde. It is even said to have been formerly grown on a large scale for medicinal. use in the neighbourhood of Deal and Sandwich in Kent. Thymol or the Camphor of Thyme was described by Neumann, apothecary to the Court at Berlin in 1725.4

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Description-The plant produces thin, woody, branching stems, bearing sessile, linear-lanceolate, or ovate-lanceolate leaves. These are 3 Booth in Treasury of Botany, ii. (1866) 1149.

1 Phil. Mag. xiii. (1838) 442.

In many of the references to thyme, Wild Thyme (Thymus Serpyllum L.) is to be understood, and not the present species.

4 Phil. Trans. No. 389.