The mild stimulating property which cocoa possesses is due to the presence of the two substances, theobromine and caffein. The presence of theobromine is peculiar to cocoa, but caffein is a stimulating principle which also occurs in tea and coffee. Whilst in the quantities in which they are present in cocoa (about 1.5 per cent. of theobromine and 0.6 per cent. of caffein) they act only as agreeable stimulants, in the pure condition, as white crystalline powders, they are powerful curative agents. Caffein is well known as a specific for nervous headaches, and as a heart stimulant and diuretic. Theobromine is similar in action, but has the advantage for certain cases, that it has much less effect on the central nervous system, and for this reason it is a very valuable medicine for sufferers from heart dropsy, and as a tonic for senile heart. That its medicinal properties are appreciated is shown by its price: during 1918 the retail price was about 8 shillings an ounce, from which we can calculate that every pound of cocoa contained nearly two shillingsworth of theobromine. _"Soluble" Cocoa._ Whilst Forster states that treated cocoa is the most digestible, experts are not in agreement as to which is the more valuable foodstuff, the pure untouched cocoa, or that which is treated during its manufacture with alkaline salts. The cocoa so treated is generally described as "soluble," although its only claim to this name is that the mineral salts in the cocoa are rendered more soluble by the treatment. It is also sometimes incorrectly described as containing alkali, but actually no alkali is present in the cocoa either in a free state or as carbonate; the potassium exists "in the form of phosphates or combinations of organic acids, that is to say, in the ideal form in which these bodies occur in foods of animal and vegetable origin" (Fritsch, _Fabrication du Chocolat_, p. 216). [Illustration: BOXING CHOCOLATES.] _Food Value of Chocolate._ I ate a little chocolate from my supply, well knowing the miraculous sustaining powers of the simple little block (from _Mr. Isaacs_, by F. Marion Crawford). Whilst the food value of cocoa powder is very high the drink prepared from it can only be regarded as an accessory food, because it is usual to take the powder in small quantities--just as with beef-tea it is usual to take only a small portion of an ox in a tea-cup--but chocolate is often eaten in considerable quantities at a time, and must therefore be regarded as an important foodstuff, and not considered, as it frequently is considered, simply as a luxury.