Another question which as yet remains a puzzle, relates to the respective shares in the general physiological action which are taken by the different ingredients of rhubarb. So lately as 1871, Nothnagel,1 a very high authority, considered that the purgative action was proved, by the experiments of Schroff, to depend chiefly on the chrysophanic acid. Theodor and August Husemann 2 take the opposite view, and think that the crysophanic acid has little or nothing to do with the purgative effect. It is worth while to review the evidence upon which these opinions respectively rest.

Schroff3 administered chrysophanic acid (obtained from the lichen called Parmelia parietina) in a dose of 8 grains; this was followed by eructation of wind and repeated semi-liquid stools, which commenced twenty-four hours after the dose was swallowed, and continued to recur for five days, during which period there were also observed loss of appetite, fulness of the head, giddiness, and dull depression. On the other hand, there is the concurrent evidence of Schlossberger, Buchheim, Meykow, and v. Auer to the effect that chrysophanic acid produces no result worth mentioning on the intestinal tract, even in the same dose (8 grains) that was employed by Schroff. Then there is a contradiction as to the cause of the color-change in the urine; Schlossberger ascribing it to the elimination of phaoretine and erythroretine, while Schroff and Buchheim always found the same coloring of the urine in their experiments with chrysophanic acid. Meykow also believes this acid always to be the cause of the color, and says that in experiments where the resinoid ingredients have seemed to produce it, this was because they contained an admixture of chrysophanic acid.

(Dr. J. Ashburton Thompson has recently made an extended series of observations with crude chrysophanic acid (goa-powder). After trial in ninety cases he concludes that in a dose of 25 grains for adults, or of six or more for children, it is an emeto-cathartic, the action of which is unattended with any inconvenient symptoms. He also made observations on a hundred and sixteen persons with pure chrysophanic acid. The action of the latter is similar to the former, with the difference that while in a suitable dose each will cause vomiting and purging, if the dose is too small, goa-powder is most likely to purge only, while chrysophanic acid is most likely to cause vomiting only.)

The great difficulty in supposing chrysophanic acid to be the cause of laxative action in rhubarb is the small proportion (2 per cent.?) in which it exists in the root. It might be imagined that fresh chrysophanic acid is generated from the chrysophane as soon as that body becomes dissolved in the gastric juice; but chrysophane itself is only present in the proportion of 1 in 1,000 of the root; it therefore appears impossible that the purgative action can be materially aided by it. It is certainly almost impossible to understand how there can be a sufficiency of the acid from any source in (say) a 30-grain dose of rhubarb to produce any decided action on the bowels, seeing that no less a quantity than 2 or 3 grains can be supposed necessary for the purpose. Nothnagel thinks it likely that the action of chrysophanic acid is increased by some of the salts present in rhubarb root; this brings to mind the old opinion that a test of good rhubarb was its containing a large number of oxalate of lime crystals, the section receiving therefrom a peculiar appearance; but this idea is now generally abandoned, although the best Russian rhubarb is undoubtedly richer in lime than are the English sorts. According to Michaelis,1 the cathartic effect is produced by the resinoid matters together with the oxalate of lime, while the chrysophanic ("rhabarberic") acid is purely tonic. Kubly2 believes that phaqretine causes a part, but only a part of the purgative action; in opposition to the idea that the remainder of that action might be due to the oxalate of lime. I may cite, moreover, the experience of the London Hospital in Pereira's time. English rhubarb was there habitually used, and found to answer well, although it contains far less oxalate of lime than the so-called Turkey sort.

1 Arzneimittellehre. 2 Die Pflanzenstoffe. 3 Wien. artzl.Woch. 1856.

If the reader will refer to the description of the various ingredients of rhubarb, he will observe that very few of them are freely soluble in water. The rhubarb tannin, to which it is impossible to attribute the purgative action, is almost the only one so soluble, except chrysophane; and this latter, as already said, is trifling in amount. On the whole, therefore, it would appear that the purgative action of rhubarb must be a compound result of several stimuli, any one of which singly would be inadequate. This must especially be the case where such a preparation as the infusion is employed; here, some 24 grains (sliced, not powdered) are infused with 2 ounces of boiling water, and virtue enough is extracted to form a draught which is mildly but decidedly laxative. Where, on the other hand, powdered rhubarb is introduced (either in pill, or partly dissolved and partly suspended in water) into the stomach, it would be more possible to imagine that some one or two of the ingredients, being thoroughly dissolved by the gastric juice, might suffice for the production of the effect. As yet, it must be confessed, we are very much in the dark. (Rutherford & Vignal, in their experiments determined that: "1. An infusion of 17 grains of Indian rhubarb when placed in the duodenum never failed to increase the secretion of bile. 2. The bile, although secreted in increased quantity, had the composition of normal bile as regards the biliary constituents proper. 3. The doses which so powerfully excited the liver, had in one case no marked purgative effect, but in two cases the purgative effect was considerable." - Brit. Med. Jour., Nov. 6, 1875.)

Therapeutic Action. - If the physiology of the action of rhubarb be still obscure, there is no doubt that the popular opinion as to the great value of the drug for several purposes is correct.

As a Laxative, in doses of 20 to 30 grains, it acts with certainty and ease; but such doses as these should not be frequently repeated, since an increasingly constipating after-effect is apt to follow; and when it becomes needful to take a mild aperient rather frequently, rhubarb should only be given in small doses, combined with other purgatives, as in Pil. Rhei comp. For a single purgative dose for children, the best plan is to combine it with one-third its weight of carbonate of soda or magnesia and a little ginger, or other carminatives, as in Gregory's powder. Unfortu-nately the gritty sensation of the powdered rhubarb is not very easily to be obviated. For adults, a pill of 6 grains of the extract with 2 grains of ginger, followed, if needs be, by a so-called " Seidlitz " draught, may answer the purpose. As a laxative in haemorrhoids, rhubarb is often very useful.

1 Journal Mens, de la Soc. Chim. de Paris. 1868. 2 Neues Rep. f, Pharm. xvii. 214.

As a Stomachic. - The stomachic uses of rhubarb are continually recurring in practice. Combined with gentian or chamomile, rhubarb, in small doses, furnishes a most valuable pill in atonic dyspepsia; an excellent stomachic may also be procured by the combination of drachm doses of the tincture with some bitter infusion, three times a day. The popular idea that rhubarb is useful in relieving pain in the bowels too often leads to mischief; for though it may be doubted if rhubarb ever originates inflammatory mischief, it can aggravate it when already existing, as in the case of chronic gastro-intestinal catarrh. When the simple union of a tonic and an antacid is required, rhubarb is often effectively combined with soda; hence 3 or 4 grains of rhubarb, with an equal quantity of the exsiccated carbonate of soda, forms a good pill for meal-times.

In Diarrhoea. - It has already been mentioned that rhubarb (like various other Polygonaceae) contains a large proportion of tannin, and this circumstance confers on it the property of restraining excessive diarrhoea with peculiar effectiveness. More especially where the diarrhoea is wholly or partly to be attributed to the operations of undigested food or other irritant matters, rhubarb acts in a twofold manner, by gently removing the offending substances, and afterwards mildly constringing the intestinal vessels, and restraining the flow of mucous secretion. On the other hand, as already mentioned, it does not appear suitable to those cases in which diarrhoea or other troublesome symptoms depend upon an inflammatory condition of the mucous membrane.

A general review of the therapeutic action of rhubarb shows that it holds a peculiar position. As a purgative it perhaps more nearly resembles aloes than anything else, but the action is milder, and it has none of that specific tendency to act upon the large intestines which distinguishes aloes. Its very remarkable tonic properties, apparently limited in their action to the stomach and intestines, stamp it as a member of a not very large class of remedies. It is not often, in the study of drugs, that one and the same medicine is found specially affecting a particular tract of the body in two entirely different modes, each of which most usefully supplements the other; but such is the case with rhubarb. A great portion of the action of rhubarb is undoubtedly exerted after its ingredients have entered the circulation. Yet it is likely that a portion of the stimulant effects upon the stomach and intestines is locally exerted before absorption. This is rendered probable from experience of its use.

As a Local Stimulant. - Sir Everard Home advised the application of pulverized rhubarb as a local stimulant to indolent ulcers; and though this plan has not been carried out to any considerable extent, the neglect arises, probably, not from its intrinsic inefficiency, but from the circumstance of there being more convenient methods of treatment.

(Crude chrysophanic acid has been in use for some time in India for the treatment of ringworm (trichophytosis). As such it was a few years since introduced to the notice of European physicians. Squire, of London, however, has recently discovered that it is one of the most effective agents we possess in the treatment of psoriasis. It is used in ointment ( 3 ss. - 3 i. to the ounce). Both in this disease and in parasitic affections we have found it exceedingly useful.)

Preparations and Dose. - Pulvis Rhei, gr. v. - xxx. (.30 - 2.); Ext. Rhei, gr. v. - xv. (.30 - 1.); Pil. Rhei, No. 1 - 5; Pil. Rhei Co., No. 1 - 5; Pulv. Rhei Co., gr. x. - xxx. (.65 - 2.); Tinct. Rhei, 3 i. - iv. (4. - 15.); Tinct. Rhei et Sennae,

Polygonageae Rhubarb Rheum Continued 8

(15. - 30.; Vin. Rhei, 3 1. iv. (4. - 15.): Ext. Rhei Fluid., m v. - xxx. (.30 - 2.); Syr. Rhei,

Polygonageae Rhubarb Rheum Continued 9

- i.

(20. - 40.); Syr. Rhei Aromat.,

Polygonageae Rhubarb Rheum Continued 10

- i. (20. - 40.); Infus. Rhei, iv. (60. - 120.).

Polygonageae Rhubarb Rheum Continued 11