This section is from the book "Practical Dietetics With Special Reference To Diet In Disease", by William Gilman Thompson. Also available from Amazon: Practical Dietetics with Special Reference to Diet in Disease.
Lemons, limes, and shaddocks may be considered together as possessing the same general properties. Owing to the potash and other salts and abundant vegetable acids which they contain, they are the most serviceable of the antiscorbutic fruits, and also afford an agreeable acid and pungent flavour to articles of diet which might become monotonous in taste. For many persons the addition of a little lemon juice to some articles of food, such as cooked cereals and porridge or broiled fish, renders them more immediately digestible, and it can be regarded as having almost a specific action in promoting gastric digestion, although it is difficult to say in just what manner this comes about. Lemons are therefore a most desirable addition to the diet kitchen.
Lemon juice is a well-known mild remedy for seasickness, and holding a thin slice of freshly cut lemon in the mouth often removes the disagreeable taste from a coated tongue, cleanses the mouth, and may even counteract nausea. Sour lemonade taken in moderation, and made quite strong by squeezing the juice of one or two lemons in a small tumblerful of water, with the addition of only one or two lumps of sugar, is a cooling and refreshing drink in fevers, and does more to diminish the craving of thirst than almost any other form of beverage.
For those who fancy effervescing drinks, the lemonade may be improved by using one of the aerated waters - such as Apollinaris, Vichy, or carbonic-acid water - instead of plain water, or effervescence may be produced by the addition of five or ten grains of sodium bicarbonate. In many cases this mild remedy is beneficial to the stomach.
Henry claims that pure lemon juice poured into the nose will often control epistaxis. Fresh lemon juice has a popular reputation for warding off rheumatism, but it has been shown to have very little influence over nitrogen elimination, although it increases the phosphates of the urine (K. Dauber).
The lime is a thin-skinned acid fruit, but there is also a sweet variety. Although less extensively eaten throughout this country than the lemon, which it resembles in effect, it is equally serviceable, and nearly ten thousand gallons of condensed lime juice are imported annually into this country from Jamaica. To make this juice the fresh limes are pressed by machinery, and the seeds and pulp are removed by straining and filtering. The juice is then boiledclown to a high degree of concentration. It is carried on sailing vessels to prevent scurvy, and used in almshouses and prisons, where the diet is monotonous.
The shaddock, pomelo, or Citrus pomelanus, is a very large, globular pulpy fruit, which may attain to a weight of fifteen pounds. The rind is thick and acid, and the very juicy pulp is bitter. The fruit keeps fresh for a long time. A smaller variety, known as the grape fruit, has come into general use of late, although it is still a relatively expensive fruit in most parts of the country. It grows in pendant clusters. Many persons find that half a grape fruit taken at the commencement of breakfast has both a laxative and diuretic action, and it is always cooling and agreeable to those who do not dislike a bitter taste. The objection to its use is that it requires a large quantity of sugar to make it really palatable and diminish its astringency. This is disadvantageous in cases of flatulent dyspepsia, but for invalids who are convalescing from prolonged fevers, suppurating disease, etc., an excellent tonic may be given by cutting a grape fruit in two and pouring half an ounce or more of good rum into the fruit, with the addition of a little sugar.
The bitterness is entirely disguised and the combination is agreeable and appetising.