116 AURANTIACE^. 



ing 2 or 3 seeds. It abounds in a pale-yellow acid juice having a 

 pleasant sour taste and a slight peculiar odour quite distinct from that 

 of the peel. When removed from the pulp by pressure, the juice appears 

 as a rather turbid yellowish fluid having a sp. gr. which varies from 

 1"040 to 1"045, and containing in each fluid ounce from 40 to 46 grains 

 of citric acid, or about 9| per cent.^ In Italy all the flne and perfect 

 fruit is exported; the windfalls and the damaged fruit are used for the 

 production of the essential oil and the juice. About 13,000 lemons of 

 this kind yield one pipe (108 gallons) of raw juice. Sicilian juice in 

 November will contain about 9 ounces of citric acid per gallon, but 

 6 ounces when aflbrded by the fruit collected in April. The juice is 

 boiled down in copper vessels, over an open fire, till its specific gravity 

 is about 1'239.^ Lemon juice (Sucmis liinonis) for administration as a 

 medicine should be pressed as wanted from the recent fruit whenever 

 the latter is obtainable. 



The peel {Cortex limionis) cut in somewhat thin ribbons from the 

 fresh fruit is used in pharmacy, and is far preferable to that sold in a 

 dried state. 



Microscopic Structure of the Peel. — The epidermis exhibits 

 numerous stomata; the parenchyme of the pericarp encloses large oil- 

 cells, surrounded by small tabular cells. The inner spongy tissue is 

 built up of very remarkable branched cells, separated by large inter- 

 cellular spaces. A solution of iodine in iodide of potassium imparts to 

 the cell-walls a transient blue coloration. The outer layers of the 

 parenchymatous tissue contain numerous yellowish lumps of a substance 

 which assumes a brownish hue by iodine, and yields a yellow solution 

 if potash be added. Alkaline tartrate of copper is reduced by this sub- 

 stance, which probably consists of hesperidin. There also occur large 

 crystals of oxalate of calcium, belonging to the monoclinic system. The 

 interior tissue is irregularly traversed by small vascular bundles. 



Chemical Composition — The peel of the lemon abounds in essen- 

 tial oil, which is a distinct article of commerce, and will be described 

 hereafter. 



Lemons, as well as other fruits of the genus Citrus, contain a bitter 

 principle, Hesperidin, of which E. Hoffmann'' obtained 5 to 8 per cent, 

 from unripe bitter oranges. He extracted them with dilute alcohol, 

 after they had previously been exhausted by cold water. The alcohol 

 should contain about 1 per cent, of caustic potash; the liquid on cool- 

 ing is acidulated with hydrochloric acid, when it yields a yellowish 

 crystalline deposit of hesperidin, which may be obtained colourless and 

 tasteless by recrystallization from boiling alcohol. By dilute sulphuric 

 acid (1 per cent.) hesperidin is broken up as follows: — 



Q22H26012 = Ci«Hi*0« . C'Hi^O^. 



Hesperidin. Hesperetin. Glucose. 



Hesperidin is very little soluble even in boiling water or in ether, but 

 dissolves readily in hot acetic acid, also in alkaline solutions, the latter 

 then turning soon yellow and reddish. Pure hesperidin, as presented 



1 Stoddart, inPliarm. Journ. x. (1869)203. ' Berkhtt der Deiitschen Chemischen Gesell- 



2R. Wariiigton, Pharm. Journ. v. (1875) sclia/t (1876) 26, 685, 693. 

 385. 



