tannate of gelatine; it, in short, tans, or converts into leather, the superficial layer of the cuticle.

The practical application of this fact is sometimes useful, as in the affections presently to be referred to. These may be classed in five divisions, according to the modus operandi of the remedy. They are those in which its curative effects depend on (a) the insensibility; (b) contraction; (c) impermeability; (d) contraction and impermeability combined; (e) removal of part, of the skin, which are caused by its application. As examples of these effects may be mentioned, (a) the relief of pain caused by external pressure on tender parts, as the integument covering abnormal projections of bone (as the spinous process of a prominent vertebra, in Pott's curvature, for example), where there exists no corresponding natural thickening of the skin, or in bunions, relieving the abnormal sensibility of the part; likewise the prevention of bedsores of any kind, if applied at the commencement before the skin breaks. (b) The binding down of the subjacent parts by contraction and slight pressure, as, for example, in weakening of the abdominal wall, and protrusion of the internal oblique muscle, by a long split in the external oblique, in the direction of its fibres (an occasional effect of falls from scaffolding, &c.,) too extensive for the truss; reducing an enlarged testicle, by first drawing the integument tense, and retaining it by means of a strap of plaster encircling tightly the cord, immediately above the gland, and applying the solution. (c) By its impermeability it checks and prevents unhealthy local sweatings. (d) By its early application it causes the absorption of matter deposited in the tissues, which may otherwise point at the surface. Its action, last mentioned in the above enumeration, (e) renders it useful in the treatment of cutaneous affections which depend on a local cause, as the layer which it forms peels off after a short time, removing, when they exist, such parasites as the pediculus pulex penetrans, acarus scabiei, entozoon folliculorum, &c. The strength of the solution of tannine required for the purposes mentioned is about 600 grains to an ounce of water. It may be applied, according to circumstances, by a layer of lint or wadding, saturated with the solution, or by means of a brush.

There are three points which must be attended to in using this remedy. Cold water must be employed, otherwise a solution of pyrogallic acid is used, not of tannine. The solution must be quite recent, and prepared in small quantities at a time; and the tannine employed must be perfectly fresh, for, unfortunately, tannine remains but a short time exposed to the atmosphere without being converted into gallic acid. It will be remembered that gallic and pyrogallic acids do not form insoluble compounds with gelatine.-British Medical Journal, March 20, 1869, p. 258.

108. THE ADVANTAGE OF ADMINISTERING COLOCYNTH IN THE FORM OF TINCTURE.

By Dr. R. W. CRIGHTON, Leamington.

The value of colocynth in cases of habitual constipation, and likewise as a revulsant in head-affection, has been long understood; but seems to have been not quite sufficiently appreciated in this country, from the drug having generally been used in the crude state.

The tincture, as employed in Prussia and admitted into the national Pharmacopoeia, is a much more agreeable and convenient method of using it; the small dose required-ten to twenty minims-being easily combined in the same mixture with tincture of hyoscyamus, bromide of potassium, or other medicinal agents. Next to croton-oil, it seems to have the greatest effect among purgatives in diminishing hyperemia within the cranium; and, in cases of threatened or actual cerebral hemorrhage, its administration with tincture of hyoscyamus and bromide of potassium, I have frequently seen attended with the best results. In habitual constipation, ten, or even five, minims in a little water an hour before breakfast generally suffice to ensure a full evacuation, without much inconvenience, or the dose requiring to be increased.-British Med. Journal, Nov. 28, 1868, p. 572.

109.-ON THE THERAPEUTICAL VALUE OF PEROXIDE OF

HYDROGEN.

By Dr. BENJAMIN W. RICHARDSON, F.R.S.

[The following paper gives a fair resumé of what is known respecting peroxide of hydrogen-its history, preparation, and therapeutical value. Peroxide of hydrogen was discovered by Baron Thénard in 1818, and he gave it the name of deutoxide of hydrogen. Since his time its nature and properties have been investigated by various chemists.]

Of late days the speculations of Schönbein relative to ozone, have caused the peroxide to be discussed more than formerly, in the way of speculative chemical philosophy.

The Preparation of the Peroxide of Hydrogen.-The chemical proposition for the formation of the peroxide of hydrogen was given by Thénard, and it stands unaltered. Gmelin thus condenses it :

When peroxide of potassium, sodium, barium, strontium, or calcium is digested in any hydrated acid which forms a soluble salt with the salifiable base resulting from the decomposition of the peroxide, the excess of hydrogen does not escape as gas, but passes over to a portion of the water, and converts it into perocide of hydrogen.

To carry out the manufacture, it is therefore necessary to obtain one of the above-named peroxides in the pure state. It has been up to this time most practicable to select out of the list the peroxide of barium, a specimen of which I hand round. This peroxide is made either by placing pure anhydrous baryta -obtained from the decomposition of the nitrate by heat-in a glass or porcelain tube, heating to redness and passing through the tube a current of dry oxygen; or by beating togther in a platinum crucible anhydrous baryta and chlorate of potassa. The first of these processes is the readiest and, I think, best. The baryta used must be freed, as far as possible, from foreign matter, particularly from manganese, and the oxygen gas must be entirely freed of admixture with carbonic acid. If either of these substances be present in making the peroxide, the result will be altogether a failure, inasmuch as both these substances have the property of evolving the oxygen with which the hydrogen is to be afterwards charged as fast as the oxygen itself is produced. The proofs that peroxide of barium is pure are these: It should present a greyish-white surface, free from green specks. Powdered and slaked with water, it should form a paste without evolution of heat. It should be entirely soluble in diluted hydrochloric acid.

In making the peroxide of hydrogen, the further processes are carried out as follows :-We take, say, twenty fluid ounces of distilled water, and add two fluid drachms and twenty minims of pure hydrochloric acid. We make the acid mix thoroughly with the water. Then we take two drachms and ten grains of the peroxide of barium, reduce it to powder, place it in a porcelain or glass basin, and pour on it a little water, until it is made into a soft paste. With a glass or boxwood knife (au iron spatula must not be used), we gently add the paste to the acid solution, stirring until all is dissolved; if a precipitate occurs, a minim or two of hydrochloric acid must be added to take up such precipitate. In this step of the process we transform the baryta into the soluble chloride of barium, and at the same time charge the water with one volume of peroxide of hydrogen. The salt of barium, which is soluble, and is in the solution, must next be removed. This is done by adding very cautiously one drachm and a half of dilute sulphuric acid. (The acid must be diluted to one part in three of water.) The sulphuric acid must be added slowly, so that heat be not evolved. The baryta will in this way be all precipitated in the form of insoluble sulphate. The solution at this stage must be set aside for a while to allow the whole of the sulphate of baryta to subside. The clear solution must be poured off as a succeeding step, and filtered through Swedish filter-paper. We have now a solution containing its own volume of peroxide of hydro

gen, as before, and again the portion of freed hydrochloric acid in lieu of chloride of barium. To this solution we re-add peroxide of barium, afterwards sulphuric acid, and so on by repetition until the water is charged with oxygen to the amount required by the operator. By care and in time water may thus be charged with thirty volumes of oxygen.

If it be required to obtain the peroxide of hydrogen in a free state by the removal of the hydrochloric acid, we pursue the steps of the process thus :

To the solution charged with the peroxide of hydrogen and the hydrochloric acid we add carefully sulphate of silver. Chloride of silver is thrown down, and the sulphate is added until precipitation ceases. The chloride of silver is then separated by filtration. The solution obtained consists of peroxide of hydrogen, water, and free sulphuric acid. The last step is to add baryta to the solution until all the sulphuric acid is fixed as a sulphate of baryta; this is removed by deposition and filtration, and pure peroxide of hydrogen remains in the water.

If it be the wish of the chemist to obtain the peroxide of hydrogen in a concentrate form, he charges a smaller portion of water, by the steps I have given above, with thirty volumes of oxygen. Then he places the solution he has made under the receiver of an air-pump with sulphuric acid around to absorb water. In this condition water uncharged with free oxygen first passes off, and at last a fluid is left which may be considered as absolute peroxide of hydrogen. It yields 475 volumes of oxygen, and evaporates under the air-pump altogether.

Simple methods of making peroxide of hydrogen have been proposed. Pelouze suggested the manufacture by adding the peroxide of barium to a solution of hydrated hydrofluoric acid. Fluoride of barium is thus thrown down, and peroxide of hydrogen is produced in solution. Taking it all in all, I consider Thénard's original process to be the best.

Therapeutical Uses of Peroxide of Hydrogen. -My first object in introducing peroxide of hydrogen into medicine was to test it as a remedy for diabetes. The theory that diabetes was a disease attended with a deficient oxidation was at one time extremely popular. I thought it, therefore, fair to ascertain whether a remedy rich in oxygen would be of service in marked cases of this disease. I soon afterwards began to test the medicine in other forms of disease, not on any particular theory of its action in every case, but if I may so say, empirically, in cases where severe and long-continued symptoms were not amenable to ordinary plans of treatment; thus in time-extending now over ten years-I have got together a large collection of facts respecting the effects of the substance in different disorders, which I will epitomise under distinct heads.

Diabetes.-I have tried the remedy now fairly in eleven cases, and in three so rigorously that nothing, I think, remained undone to make the experience crucial.

In the first of these three cases the administration of the remedy was attended with such remarkable signs of improvement that the patient (a woman) came to the conclusion that she was cured. During the first eight days the renal secretion was reduced from five to two pints, and on the eighth day the specific gravity, which had been 1045, had come down to 1023. The medicine was now suspended for four days, with immediate increase of the amount of secretion to five pints. The medicine again resumed, there was immediately a cessation of the diuresis. This continued until the eleventh day, on which day only two pints of urine were passed in the twenty-four hours. At this point symptoms of hemiplegia, which had twice before appeared, recurred, attended, as they had also been previously, with epileptiform convulsions, in the course of one of which attacks she suddenly expired. The results of this case left me in doubt as to the influence which the medicine might have had in arresting the saccharine secretions; for it has been observed by Dr. Garrod and other physicians that the elimination of sugar during diabetes is often temporarily arrested by the occurrence of new changes of disease in the system. I held the matter, therefore, open as subject to further inquiry. The quantity of solution taken by this patient averaged three fluid drachms a day; the strength of the solution was ten volumes.

The second case was that of a child 8 years of age. She had been suffering from diabetes for eight months at the time when she was presented to me. At this period the specific gravity of the urine was 1058, and the quantity passed fifty ounces per day. On October 22, she commenced to take the peroxide in drachm doses three times daily, which were to be increased to doses of three drachms; the quantity of urine passed was accurately measured, and the specific gravity taken twice daily. At the end of seven days the specific gravity stood at 1043, and the quantity passed was sixty ounces per day. The treatment was now continued for twenty-three days, the dose of peroxide being increased to half an ounce, when observations were taken for four days with the following results. On the first day the quantity of urine was seventy-seven ounces, specific gravity 1046; on the second sixty ounces, specific gravity 1041; on the third seventy-three ounces, specific gravity 1046; and on the fourth seventy-three ounces, specific gravity 1040.

For a period of four days the peroxide was withdrawn, during which time seventy-six ounces were passed daily, with a fluctuating specific gravity; the medicine was then resumed, five minims of the tincture of muriate of iron being added to