Researches upon the Jalaps.

Botanical name: 


In commercial specimens of any kind of true jalap (tuberous, fusiform, or Tampico) several varieties of tubercules can be distinguished by their external characters. Those which constitute the greater part of the jalap, and which I designate under the name of "typical tubercules," always present at one of their extremities (the upper) the remains of aerial organs. Sometimes they terminate in a point at both their extremities; sometimes one of the extremities only becomes slender, whilst the other presents a large surface of insertion. There are met with, besides, tubercules inserted on other tubercules, and very small fragments [grabeaux] showing tubercules inserted upon an organ which is most frequently slender and cylindrical, but sometimes fusiform and more or less swollen. The question presented itself to me, whether these tubercules of the different varieties answered to variations in appearance of one and the same organ, or whether they represented organs of a different morphological nature.

An examination with the naked eye, and aided by a glass, of transverse sections made at different points of these tubercules, yielded me some useful information, but not sufficient to answer the question with certainty. I then submitted the same sections to a microscopical examination.

As a basis for this micrographic study I selected a typical tubercule of the tuberous or official jalap.

A transverse section made at the lower extremity of the tubercule enabled me to conclude that the organ there presents the structure of a root. Towards the centre of the section there were observed four primary woody layers, symmetrical around the centre, and convergent in pairs. Each of these layers is formed of some spiral vessels, the most slender of which are nearest the exterior, the largest being nearest the centre. The differentiation has therefore proceeded in each of these primary ligneous layers from the centre of development (indicated by the most slender spiral vessels) towards the centre of the organ. It may thence be concluded that the centre of the organ is occupied, by a single tetracentral primary bundle, the centre of which coincides with the centre of the organ, and it may be inferred from this conclusion that the organ, at this stage, is a root.

Among the histological details presented by this root, I will refer here only to the formation of the elements of the liber. Among the young cells with tangential divisions belonging to the cambial zone the most external present very early longitudinal septa, which subdivide them into a number of narrow elongated cells, such as are seen in the Asclepiadaceae, Apocynaceae, Solanaceae and Acanthaceae. The transverse septum which separates two superposed cells is reabsorbed, following the meshes of the tissue, and in this way are originated the perforated plates of cells characteristic of the liber. The elements of the cambial zone which do not present these septa make up the liber parenchyma, in the midst of which occur numerous resiniferous cells and glands containing crystals.

The resin-cells would appear to be parenchymatous elements, hypertrophied and gorged with resin. Generally they are superposed end to end, so as to form rather long vertical rows; but in no case have I observed the reabsorption of the wall common to two successive cells. There is therefore no formation of a canal, and I look upon these resin cells as unicellular glands distributed in the mass of the liber.

The crystal-bearing glands consist of parenchymatous cells, subdivided into as many compartments as they contain groups of crystals. These groups are sphaeraphides of oxalate of lime. A radial section, treated with a mineral acid which dissolves the oxalate of lime shows readily the subdivision of these glands.

I will now briefly sketch the structure of the part of the tubercule comprised between the lower extremity and the point which corresponds to the maximum volume of the organ, setting forth the mechanism of the formation of the tuber.

In sections which follow those which presented the structure of a well-characterized root, there is observed, in proportion as they rise towards the central part of the tuber, the interposition, among the hardened and characteristic elements of the root, of a parenchymatous tissue, supplied at first solely by the cambial zone. The interposition of this tissue, which I will call the "muriform parenchyma," results in separating the woody layers from each other, and quickly interfering with the primitive symmetry of the organ. The spiral layers, carried away and twisted in every direction by the secondary ligneous lobes, quickly disappear, so that at a very short distance from the lower extremity of the tubercule it is already impossible to recognize, them.

Higher up the muriform parenchyma which surrounds the indurated ligneous masses splits up parallel to the surface of these masses, and thus originate true secondary generating zones, which produce, on the side of the wood some rows of muriform parenchyma, and, on the other side, secondary liber, with numerous glands containing resinous, and crystalline matter.

In the most swollen parts are seen important layers of muriform parenchyma, divided tangentially in every direction, and furnishing, at the same time, liber products on the one side and parenchymatous elements on the other. All the parenchymatous cells are gorged with starch, and the tubercule constitutes an important alimentary reserve for the plant.

In studying the upper portion of the tubercule I have followed the reverse order, and starting from the upper extremity descended towards. the centre.

The transverse section made at the top extremity of the tubercule shows that the organ, at this point, has the structure of a stem. The primary ligneous mass forms, in fact, an annular zone around the centre of the organ, but at a certain distance from the centre. It is formed of radiating layers grouped in badly defined bundles. Each layer of primary wood comprises three or four contiguous spiral vessels disposed radially, the most slender being inside. The differentiation of the primary ligneous elements, therefore, has proceeded from the centre of the development (indicated by the most slender spiral vessel) in a direction which passes by the centre of the organ, but which leaves the centre of development between the centre of the organ and the, ligneous layer. The centre of the organ presents, therefore, a central crown of bundles with centrifugal differentiation. From this it may be concluded that the organ at this level is a stem.

Moreover, at the top of the cicatrices, to which I have referred before, is observed the issue of four bundles, in two opposite appendages on each side. At the axil of each of these appendages a bud that is frequently developed is placed between the two bundles in relation with the bundles of the stem. In the interval comprised between the point of issue of the appendages and the swollen middle portion of the tubercule occurs the extinction of the primary ligneous layers of the stein. The organ becomes tuberized in this region by the same process as in the inferior portion.

The extinction of the primary ligneous layers of the stem shows that there is here a lower termination of the principal stem. Therefore, the stem which forms the upper portion of the typical tubercules of jalap is a principal stem, its inferior appendages are cotyledons, and their axillary buds correspond to creeping branches.

The secondary elements of the stem are in direct continuation with the secondary elements of the root; from this it follows that the root which forms the lower end of the tubercule below is the principal root. The part comprised between the points where the cotyledons issue and the point of insertion of the principal root corresponds therefore to the hypocotyledonous axis.

This investigation allows of the conclusion that the typical tubercules of jalap represent the stock of the convolvulaceous plants which produce them, and that the tuberized portion corresponds to hypertrophy: (a) of the base of the principal stem; (b) of the hypocotyledonous base; (c) of The region of insertion of the principal root upon the hypocotyledenous axis; and (d) of the upper part of the principal root.

I have studied in the same manner the various tubercules of jalap that never present the remains of aerial organs at one of their extremities, and I have in this way recognized that

(1) Most of the varieties of tubercules represent tuberized roots of different orders ;

(2) Some tubercules represent subterranean stems, which, having to play the same physiological role as the radical tubercules, are tuberized by the same process and present a nearly identical structure.

Finally, comparison of the three commercial kinds has shown me, that in respect of structure there is no difference, however slight, between the different kinds of true jalap.

From the materia medica point of view the jalaps are therefore principally formed of tubercules which correspond to the stocks of the convolvulaceous plants that produce them; they include, besides, a certain number of tubercules which represent tuberized roots of different orders; lastly, tubercules are met with derived from tuberized subterraneous stems.

I will now add some pharmaceutical observations upon jalap and the resin extracted from it.

In none of the published analyses of jalap is mention made of oxalate of lime, but a microscopic examination and microchemic tests detect it in considerable proportion in the tubercules.

I am unable to accept the opinion of M. Andouard, according to which the small roots of jalap would be generally more rich in resin than the large tubercules from the same plant. This does not agree with what is revealed by the microscopic investigation, and, moreover, is not in accord with the amounts found by M. Guibourt. Would not M. Andouard consider as "small roots" the slightly tuberized fragments which are met with in the debris, which are derived from subterranean stems and which in fact contain much resin?

With the object of adding something new to the results already known, I have extracted the resin, by the Codex process, from nine specimens of jalap. In order to utilize the products of the aqueous macerations involved in this process, I prepared extracts evaporated in a water-bath to a pilular consistence, of which I have given the yield.

Supplied by the "Pharmacie Centrale."
Resin dried
at 100 °. Per cent.
Per cent.
Tuberous or official jalap, 12.5 38.0
Light jalap (small specimens), 2.0 35.0
Digitate major jalap, 7.0 12
Digitate minor jalap, 9.0 11.5
No. 1, 12.5 35
No. 2, 10.5 33
No. 3, 7.5 23
No. 4, 8.0 17
III. DEBRIS, 8.5 27

It follows from the investigation of different authors that jalap owes its purgative properties to two homologous resinous glucosides, convolvulin and jalapin. I have, however, nowhere met with mention of clinical experiments made with the pure glucosides. Might there not be, if not an alkaloid, as alleged by Hume, at least a principle other than the resinous glucosides, and which has hitherto escaped analysis? If the opinion of La Maout and Decaisne is to be accepted (Traité général Botanique) the resin of the Convolvulaceae owes its purgative properties only to the aroma which accompanies it, for the rhizomes lose them when powdered and exposed for a long time to the air, although they preserve the purely resinous principle. The odorous oleaginous substance which floats at the top towards the end of the distillation, when nearly all the alcohol is removed from the tincture of jalap from which it is desired to extract the resin, would deserve attention from this point of view.

When jalap resin is prepared by the Codex process, and, in following the mode of operation prescribed, the residue from the distillation of the alcoholic liquor is poured into boiling water, the resin precipitated agglomerates under the form of a thick turpentine, which adheres strongly to the sides of the vessel and can only be collected completely with great difficulty. I have found that if, on the contrary, the residue from the distillation be poured into well-cooled water, the precipitated resin will remain on the sides of the vessel in a very divided form; the resinous particles are separated one from another by drops of water, and it is very easy to collect the product with the aid of a flexible spatula. Upon placing all the resin together in a small capsule the water gradually floats to the top whilst the resinous particles agglutinate.

Finally, I have compared, in respect to yield, the Codex process, which gives an odorous greenish-brown resin, and M. Nativelle's process, which gives an inodorous resin, as white as starch. The following are the results I have obtained:

Codex Process. Nativelle's Process.
Resin. Extract Resin. Extract.
No. 1, 7.0 11.5 3.0 9.0
No. 2, 12.5 33.0 6.0 27.0
No. 3, 7.5 23.0 3.3 17.0

This enormous difference in the yield of resin is due to the use of 65° alcohol, as recommended by M. Nativelle, which does not dissolve all the resin removed by 90° alcohol, as ordered in the Codex.

It is worthy of notice that more aqueous extract was obtained in evaporating the products of the macerations yielded by the Codex process than in evaporating the products of the decoctions necessitated in following the process of M. Nativelle.—Phar. Jour. and Trans., Nov. 11, 1882; from Jour de Phar.

The American Journal of Pharmacy, Vol. 55, 1883, was edited by John M. Maisch.