By incineration, we obtained ashes from the milk in which were found phosphate of lime, lime, magnesia, and silica.

During their excursions in the Cordilleras, the inhabitants fre quently drink the milk of the cow-tree. M. de Rivero and myself also used it during our sojourn at Maracaibo.

The tree which produces the milk which we examined, is, accord ing to M. de Humboldt, the galactodendron dulce, of the family of the verticas, or fig-trees. But several trees are known in the mountains along the coast, which yield a milky juice, and which are often confounded with that just described. For instance, in the

environs of Maracaibo, according to M. Desvaux,* the clusia galactodendron yields an abundance of very pleasant vegetable milk; this milk, however, does not seem to contain much animalized matter; at least it does not putrefy perceptibly, and instead of the waxy matter, a substance much less fusible and of a resinous character is procured from it.

MILKY SAP OF THE HURA CREPITANS, (AJUAPAR.)

The sap of the hura crepitans is dreaded, and not without good reason; it is enough to be exposed to the emanations of this milky juice, when recently extracted, to be seriously affected by it. The use which is made of it, to poison the water of rivers, in order to obtain the fish, is a sufficient indication of its pernicious qualities.†

This vegetable sap would perfectly resemble that of the cow-tree, if it were not slightly yellowish. It has no smell; its taste, which is very little marked at first, soon causes very violent irritation. It reddens the color of turmeric; mineral acids produce in it a white and viscous curd; the surrounding fluid is clear and of a yellow color. Left to itself, the milky sap of the hura crepitans yields all the products of the putrefaction of caseum. It contains: 1. An azotized substance similar to gluten, or caseum. 2. A vesicating oil. 3. A crystallized substance, having an alkaline reaction. 4. Malate of potash. 5. Nitrate of potash. 6. A salt of lime, (the malate) 7. An odorous azotized principle.

MILKY SAP OF THE POPPY, (OPIUM.)

The milky sap which, by concreting, furnishes the opium of commerce, is obtained by making longitudinal incisions in the capsules of the poppy. The operation takes place before the fruit is ripe, and after the fall of the flower.

* Renseignements communiqués par M. Adolphe Brongniart.

↑ Rivero et Boussingault, Annales de Chim. et de Phys. t. xviii. p. 430, 2e série. What I shall now state may give an idea of the energy with which this milky juice acts on the animal economy: when M. Rivero and myself examined the milk of the hura crepitans, we became affected with erysipelas; the affection continued for several days. The milk had been sent to us in guaduas by Dr. Roulin; the messenger who brought it was seriously affected by it; and along the road the inhabitants of the houses where he lodged felt the same effects.

The concrete sap is brown, firm, of an acrid and bitter taste, and of a peculiar sickening odor. Opium contains a number of principles, the study of which has exercised for a considerable time the ingenuity of the most skilful chemists. It was in this substance that Sertuerner found the first vegetable alkali which was discovered, morphine. After numerous trials made on opium, it was found to contain :-1. Morphine, (vegetable alkali.) 2. Codeine, (the same.) 3. Narceine. 4. Meconine. 5. Para-morphine. 6. Pseudo-morphine. 7. Meconic acid. 8. Resin. 9. Fatty matters. 10. Caoutchouc. 11. Gum. 12. Bassorine. 13. Ulmine. 14. Woody substance. 15. Mineral salts with bases of lime, magnesia, and potash.

MILK OF THE PLUMERIA AMERICANA.

The plumeria, when one of its branches is broken, yields a considerable quantity of milky juice. At the time when I examined this juice, the tree was entirely destitute of leaves. The milk of the plumeria is perfectly white; it is very fluid when it flows from the plant, but soon after deposites a crystalline sediment. The taste is slightly bitter, and it has an acid reaction. The milk of the plumeria appears to contain no animalized matter. I was only able to detect a very large proportion of resinous matter held in solution or suspended in water; and indications of potash, lime, and magnesia, combined with an organic acid.

SAP OF THE CAOUTCHOUC TREE.

Caoutchouc is found in the sap of many trees, and in that of a great number of herbaceous plants; but it is the havea caoutchouc, the jatropha elastica, peculiar to South America; the ficus Indica, and the artocarpus integrifolia, which grow in the East Indies, that yield the caoutchouc so well known in commerce, and which has been converted to so many useful purposes in the arts.

The caoutchouc tree is particularly common in Choco and forests near the equator. To obtain the elastic gum, the Indians incise the tree below the bark, when there issues a copious discharge of milky sap, which will remain fluid for a considerable time, if it be kept from contact with the air. I have seen I have seen it carried to great distances, in wooden vessels hermetically closed. When spread out in thinnish layers, it soon coagulates, and acquires the singular elasticity which characterizes caoutchouc. The action of the oxygen of the air may possibly have some influence in producing this coagulation, unless what I am about to state be the effect of a prompt evaporation of the water of the sap. I have often made a small incision in the trunk of an hævea from which milk immediately flowed, and by reason of its viscidity, trickled down the tree in a stream of a certain thickness; this milk was at first extremely fluid, but after from one to two minutes' exposure to the air, it suddenly coagulated, so that on raising the drop from the lower end, I obtained a long string or riband of perfectly elastic caoutchouc.

In Guiana the Indians fashion the caoutchouc into the bottles which are so common in trade: they make a clay mould, and this they cover by immersing it in the milk freshly drawn from the tree; they allow it to coagulate, which it does very speedily, especially if it be exposed to the smoke of a wood fire. This first layer being coagulated, they continue the same process until the desired thickness is attained. The mould is then broken and taken out piece-meal from the interior of the caoutchouc bottle which has been formed.

The workmen of Quito, who are very dexterous in manufacturing caoutchouc, make shoes and buskins of it, by applying it in the milky state over moulds of the proper fashion. They also render tissues impervious by spreading it in the same state between two pieces of stuff or cloth; the interposed milk becomes coagulated, and forms a thin elastic lamina, very preferable to the caoutchouc applied by the aid of solvents.

The Indians of Choco sometimes procure this substance by felling the tree, and receiving the milk, which then flows in a stream, into large wooden moulds, generally formed from a hollow stem of the guaduas. By keeping the mould open, the milky mass coagulates after some time. Several of these masses of caoutchouc, which were brought to me by the Indians of the Chami nation, were but slightly elastic; their color also was extremely deep. It is probable, that by proceeding in this way, the milky juice is mixed with large quantities of the internal sap which is much less milky.

Several trees in the valley of the Magdalena which bear the name of caoutchouc, which, however, are neither the hævea, nor the jatropha, also yield a coagulable juice, which may be confounded with the elastic gum; it is, I believe, caoutchouc combined with a large quantity of wax, and probably also of resin; this caoutchouc possesses but little elasticity.

M. Faraday found in the milk of the hævea, in 100 parts:

As this milk will remain fluid for a considerable time, provided it ne protected from the air, advantage has been taken of this property to convey it to Europe. It is sent in well-filled, hermetically-sealed bottles.

GUMMY AND RESINOUS SAPS.

I place under this head the saps of those trees which yield gum from incisions in their trunk, as the acacia vera and acacia Arabica, which grow in Arabia, and from which gum-arabic is obtained; acacia Senegal, which also furnishes a species of gum. In general, in very warm countries, the mimosas produce gummy matters in abundance.

The elaborated sap of the coniferæ and terebinthaceæ consists thiefly of resinous matter, dissolved in an essential oil composed of

carbon and hydrogen, similar to the essence of turpentine. The balsams of Peru and Tolu are obtained by incising the bark of the trees which produce them. In Choco, where I have seen numerous incisions made in the lower part of the trunk of the Tolu trees, the balsam flows slowly, on account of its thickness; it does not, apparently, contain any water.

SACCHARINE SAPS.

At

The sap of the fraxinus ornus, and that of the fraxinus rotundifolia, yield manna on drying or becoming thick. The sap of several palms contains a considerable quantity of saccharine matter. Java, for instance, crystalline sugar is extracted from the arenga saccharifera. In several places, the sap of palm-trees is subjected to fermentation in order to prepare vinous liquors.

The Cocos butyracea (palma de vino) is very common in the valley of the Rio-Grande de la Magdalena. From a superficial examination which I made of it, its sap contains sugar, an azotized matter, and some soluble salts.

By fermentation, it produces a vinous liquor sufficiently alcoholic to produce intoxication. In order to procure it, the natives of Benadillo first fell the tree, taking care, when it is down, to give the trunk a slight inclination from the summit towards the lower extremity or foot. They then make a hole towards the base of the trunk sufficiently large to hold from fifteen to eighteen pints, the orifice of which they plug up with leaves. The woody tissue, to all outward appearance, contains but little moisture; but in ten or twelve hours after the operation, the cavity is found full of a liquid, of a wellmarked vinous odor, and of a sourish taste, owing probably to the carbonic acid which is disengaged in large quantity. The wine thus obtained is rather agreeable. A palm-tree of from 50 to 60 feet in height, and of which the trunk towards the base is from 20 to 24 inches in diameter, will yield from twenty to thirty pints of wine in twenty-four hours during ten or twelve days. The wine must not be allowed to remain too long after it has collected, otherwise it becomes sour.

Sugar is far from being the only useful substance afforded by palms. There are several of these trees which are truly astonishing by reason of the many important uses to which they may be applied ; and it is not without reason that the missionaries have styled the palm, the tree of Providence, the bread of life. Such more especially is the Cocos mauritia, which grows in the plains of the Apure and Oronoko; its young shoots serve as aliment; from its fruit, while still green, a farinaceous food may be obtained; and when perfectly ripe, it yields oil in abundance. Hammocks and various kinds of cloth are made of the fibrous portion of the bark of this tree; the young leaves serve to make hats, mats, and sails for ships; the tissue which surrounds the fruit furnishes the Indians with clothing; the sap ferments and yields wine; the trunk before fructification contains an amylaceous marrow, of which bread is made; this marrow, on becoming putrid, produces a vast multitude of large

white worms which the Indians value as a most delicate dish; finally, the woody part of the mauritia affords excellent timber for building. It is not necessary to enumerate farther the principles produced by vegetables; we must now study them in reference to their elementary composition.

CHAPTER II.

OF THE CHEMICAL CONSTITUTION OF VEGETABLE SUBSTANCES.

FROM the very first period of vegetable life, during germination, the immediate principles which constitute the seed are destroyed or changed. The young plant, in developing its organs, creates new substances, which are added to the tissues already existing, so as to complete or extend them. In order to account for the productions or changes which take place in the organism of vegetables, it is expedient first to study the intimate nature and general characters of the materials which compose them. Unfortunately, in the present state of science, this study is as yet but little advanced; and, notwithstanding the efforts which chemical physiology has made in recent times, there still remain numerous and important questions to be solved.

Carbon, hydrogen, oxygen, azote, combined in some cases with minute quantities of sulphur or phosphorus, are the only elements required by nature to give rise to that almost endless variety of vegetable substances, so different in their properties, as well as in their uses. In the food which sustains the life of animals, as in the virulent poison which destroys it, these same elementary bodies are always found combined in various and dissimilar proportions.

The immediate principles of the vegetable kingdom may be divided into three groups, if we look to the number of the elements which constitute these principles as they exist in the several bodies: 1°. Quarternary, containing carbon, hydrogen, oxygen, azote. 2o. Ternary, containing carbon, hydrogen, oxygen.

3°. Binary, containing carbon and hydrogen, or carbon and oxygen, or carbon and azote.

It is by the examination of the immediate principles which exist in the seed, that we should approach the study of the composition of vegetables; and this the more, as we shall find these principles diffused throughout the organs of plants. Once we shall have fully considered their properties and their elementary composition, it will be sufficient merely to indicate where they are to be met with in the organism.