284 MYRTACE^. 



but lias its internal tissue far more porous than the walls. The whole 

 calyx is of a deep rich brown, has a dull wrinkled surface, a dense 

 fleshy texture, and abounds in essential oil which exudes on simple 

 pressure with the nail. Cloves have an agreeable spicy odour, and a 

 strong biting aromatic taste. 



The varieties of cloves occurring in commerce do not exhibit any 

 structural differences. Inferior kinds are distinguished by being less 

 plump, less bright in tint, and less rich in essential oil. In London 

 price-currents, cloves are enumerated in the order of value thus: 

 Penang, Bencoolen, Amboyna, Zanzibar. 



Microscopic Structure — A transverse section of the lower part of 

 a clove shows a dark rhomboid zone, the tissue on either side of which 

 is of a lighter hue. The outer layer beneath the epidermis exhibits a 

 large number of oil-cells, frequently as much as 300 mkm. in diameter. 

 About 200 oil-cells may be counted in one transverse section, so that 



iiount of essential oil in the drug is well shown by its 



the large amount 

 mici 



J. — ..^..*..^xo. The above-mentioned zone is chiefly made up 



of about 30 fibro-vascuhir bundles, another stronger bundle traversing 

 the centre of the clove. The fibro-vascular bundles, as well as the tissue 

 bordering the oil-cclLs, assume a greenish black hue by alcoholic per- 

 chloride of iron. Oil-cells are also largely distributed in the leaves, 

 petals and even the stamens of Eugenia. 



Chemical Composition — Few plants possess any organ so ricjim 

 essential oil as the drug under consideration. The oil known m phar- 

 macy as Oleitm Cain/ovhvlli. which is the important constituent o 



cloves, is obtainable to the extent of IG to 20 per cent. But to extract 

 the whole, the distillation must be ' long continued, the water bein^ 



returned to the same material. 



irneu to tne same material. „ , , ,,. 



The oil is a colourless or yellowish liquid with a powerful odour 

 and taste of cloves, sp. gr. 1-04C to I'OoS. It is a mixture of a lijaro 

 carbon, and an oxygenated oil called Eugenol, in variable proportioa-^ 



termed ligJit oil of 



has 



0-918 and boils at 251° 0. It deviates the plane of polarizatioii slignj 

 to the left, and is not coloured on addition of ferric chloride ; it is » 



Jl I 1»|-1B __ 



rather terebinthinaceous odour. 



aiui otjieuiuuunaceous oaour. „ . /^nl7 ^t 



Eugenol, sometimes called Eugenic Acid, has a sp. gr. ot i ^ 

 C, and possesses the full taste and smell of cloves. "^ J^ ^ i| 

 r -int is 247°-5. With alkalis, especially ammonia and baryta it V 

 crystallizable salts. Eugenol may therefore be prepared by su'^^i , -^jj 



distillation 



^y^^ v.iuut^ uii oi Cloves 10 custiiiation witn causuc ou^c^, -- ij^jj^^^ 

 oil " distils then, the eugenol, being now combined with so ^^^.^ 

 remains in the still. It will be obtained on addition of an acid an^^ ; ^' ji 



distillinLj. 



O 



ot cloves, of which eugenol is by far the prevailing constiuu, ^^^ 

 optically almost inactive. The constitution of eugenol is given dJ' 



formula C^H^ J OH .It belongs to the pbenol class, and has 



^ ^ lCH.CH.CH' ,. , , next 



also been met with in the fruits of Pimenta officinalis (see ^^^ 

 article), m the Bay leaves, in Canella bark (see page l^h 



