thus obtained contains the pure gastric juice, with much epithelium from the glands and surface of the mucous membrane. It is to be spread out upon a piece of glass, so as to form a very thin layer, which is to be dried at a temperature of 100° over hot water, or in vacuo over sulphuric acid. Care must be taken that the temperature does not rise much above 100°, because the action of the solvent would be completely destroyed. When dry the mucus is scraped from the glass, powdered in a mortar, and transferred to a well-stoppered bottle. With this powder a good digestive fluid may be made as follows:

Macerate it at a temperature of 100° for an hour. The mixture may be filtered easily, and forms a perfectly clear solution very convenient for experiment.

If the 'powder is to be taken as a medicine, from two to five grains may be given for a dose, a little diluted hydrochloric acid in water being taken at the same time. The pepsin powder may be mixed with the salt at a meal. It is devoid of smell, and has only a slightly salt taste. It undergoes no change if kept perfectly dry, and contains the active principle of the gastric juice almost unaltered.

The method of preparing this pepsin was communicated to Mr. Bullock, of the firm of Messrs. Bullock & Reynolds, 3, Hanover Street, Hanover Square, who at once adopted it for the preparation of medicinal pepsin, and soon improved upon it in some particulars. The dose is from 2 to 4 or 5 grains. Test: 8 grain of this pepsin, with 10 drops dilute hydrochloric acid and an ounce of distilled water, dissolve 100 grains of hard-boiled white of egg in from twelve to twenty-four hours."

Preparation of Pepsin. E. Scheffer. (Amer. Journ. Pharm., and Pharm Journ., 3rd series, ii., 761, 784.) The author finding that an infusion of the mucous membrane of fresh pigs' stomachs, prepared with water acidulated by muriatic acid, is precipitated by chloride of sodium and other soluble salts, and that the precipitate so formed, when pressed and dried, possesses powerful digestive properties, adopted the following process for making pepsin :

Preparation of Pepsin.-Of the well-cleaned fresh hog stomach the mucous membrane is dissected off, chopped finely, and macerated in water acidulated with muriatic acid for several days, during

which time the mass is frequently well stirred. The resulting liquid, after being strained, is, if not clear, set aside for at least twenty-four hours in order to allow the mucus to settle. To the clarified liquid the same bulk of a saturated solution of sodium chloride is added, and the whole thoroughly mixed. After several hours the pepsin, which by the addition of chloride of sodium has separated from its solution, is found floating on the surface, from whence it is removed with a spoon, and put upon cotton cloth to drain; finally it is submitted to strong pressure, to free it as much as possible from the salt solution.

The pepsin, when taken from the press and allowed to become air dry, is a very tough substance, and presents, according to thickness, a different appearance, resembling in thin sheets parchment paper, and in thick layers sole leather; its colour varies from a dim straw yellow to a brownish yellow. Besides a little mucus, it contains small quantities of phosphate of lime and chloride of sodium, which, however, do not interfere with its digestive properties, as they are found also in normal gastric juice.

Saccharated Pepsin:-To work it into saccharated pepsin (American Journal of Pharmacy, January, 1871), the damp pepsin, as it is taken from the press, is triturated with a weighed quantity of sugar of milk to a fine powder, which, when it has become air dry, is weighed again, the quantity of milk sugar subtracted and so the amount of pepsia found. The strength of this dry pepsin is now ascertained by finding how much coagulated albumen it will dissolve at a temperature of 100° F. in five or six hours, and after this sufficient milk sugar is added to result in a preparation of which ten grains will dissolve one hundred and twenty grains of coagulated albumen; and this preparation I have called saccharated pepsin.

Purification of Pepsin.-Anxious to get the pepsin in its purest state, if possible chemically pure, I tried different methods, but have not succeeded as yet. In order to get a purer article I redissolve the pepsin, as obtained after expression, in acidulated water, filter the solution through paper, and precipitate again with a solution of sodium chloride; the precipitate, after draining and pressing, is now free of phosphate of lime and mucus, but still containing salt. In the freshly precipitated state the pepsin is very readily soluble in water, and cannot therefore be freed from adhering salt by washing.

By allowing the pressed sheet of pepsin to get perfectly air drywhereby it becomes coated with a white film and small crystals of

chloride of sodium-and by immersing it then in pure water for a short time, the greater part of sodium chloride can be extracted, but it has to be done very rapidly, as the pepsin swells up considerably and loses its tenacity. By operating in this manner I have obtained a pepsin which dissolves in acidulated water to quite a clear colourless liquid, but as it still contains traces of salt, I prefer to call it purified pepsin.

I obtained a pepsin quite free of chloride of sodium-which by combustion did not leave any ash-by swelling purified pepsin in water to a thick mucilaginous liquid, and mixing it with alcohol of 95 per cent. A gelatinous almost transparent precipitate is formed, which is put on a cloth, washed with diluted alcohol, then pressed and dried. This preparation did not leave any ash by combustion; but I was greatly disappointed in my expectation, when I found that the digestive strength of this pure pepsin was not as great as that of the purified pepsin which still contained sodium chloride. No doubt the use of alcohol had impaired the digestive power of the pepsin to some extent.

Properties of Pepsin.-The pepsin is, as already mentioned, very soluble in water when recently precipitated, but when once air dry it dissolves but slowly and only in very small quantities in water.

The dry purified pepsin, when put into water, swells up considerably, becomes perfectly white, and when vigorously shaken, disintegrates to small floccules, which swim in the liquid and remain suspended for a long time, while a very small quantity will dissolve.

The watery solution has an almost neutral reaction, is coagulated by boiling, and gives with alcohol a transparent, gelatinous precipitate.

The precipitate formed by chloride of sodium is very characteristic and at the same time very interesting. When a saturated solution of chloride of sodium is added to a clear solution of pepsin, not too concentrated, at first a jelly-like transparent coagulation is formed, which disappears upon stirring, and the liquid acquires a slightly opalescent appearance; after a short time it becomes more turbid, and small flakes are noticed floating in it, which soon will form into small transparent globules, and as such rise to the surface. When the quantity of pepsin in a liquid is very small, the opalescence and turbidity is hardly noticed, but after some time the small globules will appear on the surface.

The watery solution of pepsin shows very little action on coagulated albumen: a certain quantity of albumen, which by a

watery solution was hardly acted upon in twenty-four hours, was readily dissolved after addition of a few drops of hydrochloric acid. A watery extraction of the mucous membrance was also experimented with, with the same result; before the addition of hydrochloric acid it did not dissolve albumen; after acidulating it the albumen dissolved easily.

Modified Pepsin.-A solution of carbonate of soda carefully added to a solution of pepsin produces a precipitate which, upon being separated from the liquid, will prove to be pepsin; but a little more carbonate of soda will redissolve it again, and the liquid no longer contains pepsin; that is, the pepsin is destroyed or modified.

An alkaline (modified) pepsin solution does not get precipitated by chloride of sodium, but upon addition of hydrochloric acid, a copious gelatinous precipitate will be immediately formed.

Digestive Power of Pepsin.-In my recent experiments I determined the strength by ascertaining the amount of albumen that would be fully dissolved in a certain time and at a given temperature. I had found that the solvent power of pepsin is not in inverse proportion to the time; for if a pepsin dissolves aæ albumen in s time, 2a pepsin will not dissolve x albumen in time, as might be supposed, but require longer time. The last portion of coagulated albumen to be dissolved in an experiment requires much longer time in proportion, even when pepsin is in excess.

The author made experiments with a solution containing 6 drops of hydrochloric acid to the fluid ounce of water, at a temperature of 100° to 105° F., and each vial was shaken about every ten minutes.

One grain of purified pepsin in 4 oz. of acidulated water was found to dissolve 400 grs. of coagulated albumen in eighteen hours at 75° F.

One grain of purified pepsin in 4 oz. of acidulated water dissolves 500 grs. coagulated albumen at a temperature of 105° F., in six hours.

Ten grains of saccharated pepsin dissolve 120 grs. of coagulated albumen in four to six hours, at 100° F.

Although I did not succeed in preparing a pepsin like Wasman's, of which one part was capable of dissolving 60,000 parts of coagulated albumen, I found that the digestive power of pepsin was almost inexhaustible.

With one-half grain of purified pepsin in 2 oz. of acidulated water I dissolved 250 grains of coagulated albumen; to the solution was added another ounce of acidulated water and 250 grs. of al

bumen; when it was again dissolved I added acidulated water and albumen in the same proportions, until finally the one-half grain had dissolved 1500 grs. of coagulated albumen. That it would have dissolved still more I proved in an experiment mentioned hereafter.

Pepton Solution.-When the albumen, which by the digestive process is converted into albuminose or pepton, is perfectly dissolved, the resulting pepton solution is a very limpid, thin, slightly yellowish-coloured liquid, which, when filtered, has an opalescent

appearance.

By addition of alcohol it remains at first clear, but forms, after twenty-four hours, a gelatinous precipitate.

Pepton Precipitate.-An equal volume of saturated salt solution added to the pepton solution produces a copious, perfectly white precipitate, which, upon being collected on a filter, drained, pressed, and dried, yields a hard white substance containing pepsin, pepton, chloride of sodium, and a little acid. Put into water it becomes translucent, like horn, and dissolves after some time.

Its solution has an acid reaction, and is not coagulated by heat; hydrochloric acid produces a heavy precipitate which, by dilution with water or by addition of more acid, will redissolve; with alcohol it becomes opalescent, and forms after some time a precipitate.

Bichloride of mercury gives a heavy white precipitate.

Coagulated albumen put into the watery solution is hardly acted upon, but when acidulated with hydrochloric acid it is dissolved.

Digestive Power of the Pepton Precipitate.-The digestive power of the precipitate, obtained by addition of sodium chloride to the pepton solution is remarkable. In many cases a solution of 1 gr. of the precipitate in 1 oz. of acidulated water dissolved 100 grs. of coagulated albumen.

With 20 grs. of saccharated pepsin in 2 oz. of acidulated water I dissolved 240 grs. of coagulated albumen; the precipitate obtained from this solution by chloride of sodium weighed, when dry, 12 grs., of which 1 gr. dissolved 100 grs. of coagulated albumen; from this last solution again, by chloride of sodium, 10 grs. of precipitate were obtained, of which 1 gr. dissolved between 20 and 30 grs. of coagulated albumen. In this way the 20 grs. of saccharated pepsin, for which I only claim the power to dissolve 240 grs. of albumen in six hours, dissolved at the rate of between 4000 and 5000 grs.

The solution of 1500 grs. of albumen, obtained by fractional