with the latter substance. The benefits experienced from the use of cocoa are due, in part at least, therefore, to the theobromine it contains. The proportion of this substance in the cocoa bean is small, but it has not yet, I believe, been rigorously determined. It exists, also, in sensible quantity in the husk of the bean. The decoction obtained by boiling the husk in water, will not, therefore, be wholly devoid of useful ingredients, or of good effect.

Third, The predominating ingredient in cocoa, and the one by which it is most remarkably distinguished from tea and coffee, however, is the large proportion of fatty matter known as cocoa-butter which it contains. This amounts to upwards of one-half the weight of the shelled or husked bean. Consumed in either of its more usual forms, therefore, cocoa is a very rich article of food, and for this reason it not unfrequently disagrees with delicate stomachs. It is in some measure to lessen the sense of this richness, that sugar, starch, and fragrant seasonings are so generally ground up with the roasted bean in the manufacture of cocoa and chocolate.

Fourth, It contains also a large proportion both of starch and gluten,-substances which, as we have elsewhere seen, form the staple constituents of all our more valuable varieties of vegetable food. The average composition of the entire bean, when deprived of its husk, is nearly as fol lows:

This composition reminds us of the richest and most nutritive forms of vegetable food; and especially of the seeds and nuts with which cattle are fed and fattened.

y

Of

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all the varieties of human food, however, it has the closest resemblance to milk. Thus, dried milk (milk evaporated to dryness), and the dry cocoa-bean, consist respectively of

It is rich, therefore, in all the important nutritious principles which are found to co-exist in our most valued forms of ordinary food. It differs from milk chiefly by the greater proportion of fat which it contains, and hence it cannot be used so largely without admixture as the more familiar milk. When mixed with water, however, as it is usually drank, it is more properly compared with milk than with infusions of little direct nutritive value, like those of tea and coffee. And, on the other hand, it has the great advantage over milk, over beef-tea and other similar beverages, that it contains the substance theobromine, and the volatile empyreumatic oil. Thus it unites in itself the exhilarating properties of tea with the strengthening and ordinary body-supporting qualities of milk. The cocoa, as shown in the above table, is richer in fat, the milk in casein. Hence probably has arisen the practice of making milk-cocoa, in which the constituents of the one ingredient dovetail into and assuage the influence of those of the other. The large proportion of oil it contains justifies also, as fitting it better for most stomachs, the practice of mixing or grinding up the cocoa with sugar, flour, or starch, in the preparation of cocoa-paste or chocolate. Both practices are indeed skilful chemical adjustments, made without chemical knowledge, as the results of long and wide experience. And, lastly, the general composition of the beans shows that, in chocolate cakes and com

fits, when faithfully prepared, there should reside, as expe rience has also shown to be the case, much nutritive virtue, and the means, both of supporting the bodily strength, and of sustaining the nervous energy reduced into comparatively small compass.

2o. BRAZILIAN COCOA, or Guarana.-In Brazil the seeds of the Paullinia sorbilis are collected, prepared, and used in the same way as those of the Theobroma cacao. They are usually described by travellers as a variety of coffeebut the seeds, like the cocoa bean, are pounded and made into cakes, which are known as Guarana bread. When used, these cakes are mixed with water, as we do with the cakes of cocoa or chocolate, and the mixture is sweetened and drank. To what extent this article is prepared and consumed in Brazil, I have not been able to ascertain. It is a fact of great interest in regard to this substance, and one which shows it to have a true place among the beverages of which we are now treating, that like tea and coffee it has been found to contain theine, and is, therefore, capable of exercising upon the system an influence similar to that which is experienced by those who use these two favourite beverages.

3o. OTHER COCOAS.-The substances, as yet known, which can be employed in the place of, or as substitutes for, Mexican cocoa, are comparatively few in number. To fit them for this purpose, they must contain an odoriferous principle of some degree of fragrance, abundance of fat, and a considerable amount of ordinary nutriment. Oily seeds and nuts are almost the only vegetable productions from which beverages resembling cocoa have anywhere been manufactured. Among these the earth-nut (Arachis hypogœa), a kind of oily underground pea, is roasted in South Carolina, and then prepared and used in the same way as chocolate. In Spain, the root of the Cyperus esculentus, or earth

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chestnut, is roasted and used as a substitute for both coffee and chocolate, but especially for the latter, which is much consumed in Spain. These are all the professed substitutes for the cocoa-bean with which I am acquainted. Neither

of the two last-mentioned, however, contains a bitter principle rich in nitrogen, of the nature of the theobromine of the true cocoa, or of the theine contained in guarana. They can never, therefore, be employed effectively to replace the Mexican cocoa.

As adulterating materials, the substances chiefly employed by fraudulent manufacturers of cocoa and chocolate, are the husks of the bean, starch, sugar, fat, ground roots, and red ochre.

Before I leave this subject, it may interest the reader if I briefly sum up what appears to be the actual state of our knowledge regarding the chemistry and physiology of the beverages we infuse.

First, As to the chemistry of the various leaves and seeds we have mentioned, it appears that, when roasted and ready for use, they all contain,

a. A volatile, odoriferous, aromatic oil, which does not exist in the fresh leaf or seed, but is produced or developed during the roasting. In tea this oil is most abundant, in coffee probably next, and in cocoa least in quantity. In the teas (Chinese and Paraguay), and in roasted coffee, the quantity and activity of this oil appear to diminish by keeping. In raw coffee, on the other hand, the power of developing this oil by roasting is greater the longer the bean is kept or allowed to ripen.

b. A peculiar, bitter, crystallisable principle, containing much nitrogen, and exerting a specific action on the system. In the teas, in coffee, and in guarana, this principle is theine, which contains 29 per cent. of nitrogen; in cocoa it is theobromine, which contains 36 per cent. of nitrogen. Weight

for weight, the average qualities of tea contain about twice as much theine as the average qualities of coffee, but in both it varies between 1 and 5 per cent. as extremes. In cocoa the proportion of theobromine has not been determined. In well-roasted coffee, and in chicory, another bitter principle, which is soluble, uncrystallisable, and free from nitrogen, ist produced during the roasting. The quantity and properties of this substance have not been determined.

c. A variety of tannin or tannic acid, which gives their astringency to the infusions prepared from all these substances. Of this ingredient the teas contain most, coffee next, and cocoa the least. The tannin of Chinese tea gives a black, that of maté and of coffee a green, with solutions containing iron.

d. A nutritious substance resembling the gluten of wheat or the fibrin of beef. In the tea leaf this ingredient is most abundant, in cocoa next, while coffee contains the least. It dissolves but sparingly in water, and is therefore generally lost to the consumer when only the infusion is drank. The full benefit of this ingredient is obtained only when the tealeaves are eaten, when the coffee grounds are taken along with the infusion, or when the whole material is made into a beverage, as in the usual modes of preparing cocoa and chocolate.

e. A quantity of fat, which in cocoa forms more than half the whole weight of the bean, in coffee one-eighth, and in tea only 3 or 4 per cent. The presence of so large a proportion of fat gives a peculiar character to cocoa, rendering it most nutritious, especially when made with milk, to those whose stomachs will bear it, but making it less suitable at the same time to persons of weak digestive powers.

Of the infusions themselves which are yielded by the dif ferent varieties of tea, maté and coffee, it is to be observed that they vary in strength with the sample employed. Of