are transparent, except at one point. Fifthly, and lastly, within the germinal vesicle and close to its surface, is an opaque spot, whose diameter is only about To or of a line: this is termed the germinal spot, or germinal spot of Wagner. The germinal vesicle and spot form the essential parts of the ovum ; it is at the latter that the development of the embryo commences. These parts of the ovum will be impressed upon the memory by arranging them in a tabular form." P. 895.

The extracts we have given will enable our readers to judge of the general scope and execution of the "Text-Book," which we can with much satisfaction recommend to those for whose assistance it is more especially designed, feeling assured that the student will here find, in addition to the ordinary contents of works of this class, a large number of important facts relating to the higher branches of anatomical science.

I. THE PHARMACOPEIA OF THE ROYAL COLLEGE OF PHYSICIANS
OF EDINBURGH. 12mo. pp. 217. Edinburgh, 1839.
The Second Edition of the above, 1841.

II. A DISPENSATORY, OR COMMENTARY ON THE PHARMACOPOEIAS
OF GREAT BRITAIN, &c. &c. By Robert Christison, M.D.
F.R.S.E. Professor of Materia Medica in the University of
Edinburgh, Vice-President of the College of Physicians, &c.
8vo. pp. 978. Edinburgh, 1842.

III. THE LONDON DISPENSATORY, &c. &c. By Anthony Todd Thomson, M.D. F.L.S. Professor of Materia Medica, Therapeutics and Medical Jurisprudence in University College, London, Fellow of the Royal College of Physicians in London, &c. &c. Svo. pp. 1317. London, 1844.

[Continued from page 219.]

WITHOUT further preface we continue our examination of the Edinburgh Pharmacopoeia, and of Dr. Christison's and Dr. Thomson's Dispensatories.

Ferri Sulphuretum.-The following are the directions of the Edinburgh College for preparing this compound :—

"FERRI SULPHURETUM.

The best Sulphuret of Iron is made by heating an iron rod to a full-white heat in a forge, and rubbing it with a roll of sulphur over a deep vessel filled with water to receive the fused globules of sulphuret which form. An inferior sort, good enough however for pharmaceutic purposes, is obtained by heating one part of sublimed sulphur and three of iron-filings in a crucible in a common fire till the mixture begins to glow, and then removing the crucible and covering it, until the action, which at first increases considerably, shall come to an end."

The process of the Dublin Pharmacopoeia, is as follows:

"Let an iron rod be heated to whiteness in a very strong fire, urged by bellows, and being immediately removed from the fire, let it be applied to a solid mass of sulphur. Let the Sulphuret of Iron received in water be separated from the Sulphur, then dried and kept in close vessels."

These processes are mixed and metamorphosed by Dr. Christison in the following manner :—

"FERRI SULPHURETUM, E. D. Protosulphuret of Iron. Sulphuret of Iron. PROCESS, Edin. Take of

Iron-filings, three parts;
Sublimed sulphur, one part.

Mix them thoroughly; heat the mix-
ture in a covered crucible till it become
red hot; remove the crucible from the
fire and allow the action to go on with-
out heat.

PROCESS, Edin. Dub. A purer sulphuret may be obtained by heating an iron-rod to a white heat in a blacksmith's forge, applying a stick of sulphur to the end of the rod, and collecting in water the fused globules which fall down. These should be freed of sulphur and kept in a close vessel."

Dr. Christison observes, that the Sulphuret which is prepared from ironfilings by one of the Edinburgh processes, contains an excess of iron; this excess is indeed so obviously great that it is singular it should have been directed to be employed. Protosulphuret of iron consists of one equiv. of sulphur 16+ one equiv. of iron 28, and supposing no sulphur to be sublimed or burnt in the operation, the result of it must consist of 44 parts of sulphuret and 20 of iron; so that when 16 of sulphur are heated with 48 of iron, the mass must consist of 44 parts of sulphuret mixed with 20 parts of iron; and when 64 grains are acted upon by dilute sulphuric acid, the gas obtained is a mixture of about 46 cubic inches of sulphuretted hydrogen, and 33 cubic inches of mere hydrogen. It is indeed true that the hydrogen does no absolute mischief, but the escape of this gas, especially when mixed with sulphuretted hydrogen, is always disagreeable; added to which, about four-tenths of the sulphuric acid employed in liberating this mixture of gases is wasted.

Dr. Thomson has entirely omitted the Dublin process; with respect to the Edinburgh formulas, he says, "the result of the first contains an excess of iron: it is only by the first process, carefully executed, that a pure sulphuret is obtained." We need hardly observe that the remark should have been, that the result of the first process contains no excess of iron; it is the second which does so.

The directions

Ferrugo is the preparation which we shall next notice. for obtaining this substance, which we find in the index is translated Rust of Iron, is thus given in the Edinburgh Pharmacopoeia.

"FERRUGO.

Take of Sulphate of Iron, four ounces:

Sulphuric Acid (commercial) three fluidrachms and a-half;
Nitric Acid (D. 1380), nine fluidrachms;

Stronger Aqua Ammonia three fluidounces and a-half.

Water, two pints;

Dissolve the Sulphate in the water, add the Sulphuric acid, and boil the solution; add then the Nitric acid in small portions, boiling the liquid for a minute or two after each addition, until it acquires a yellowish-brown colour and yields

a precipitate of the same colour with ammonia. Filter; allow the liquid to cool; and add in a full stream the Aqua Ammoniæ, stirring the mixture briskly. Collect the precipitate on a calico-filter; wash it with water till the washings cease to precipitate with nitrate of baryta; squeeze out the water as much as possible; and dry the precipitate at a temperature not exceeding 180°. "When this preparation is kept as an antidote for poisoning with arsenic, it is preferable to preserve it in the moist state, after being simply squeezed."

Dr. Christison, in his Dispensatory, has accidentally substituted three fluidounces and a-half of sulphuric acid for three fluidrachms and a-half. It will be remembered that, in preparing the Ferri oxidum nigrum, the protoxide of half of the sulphate of iron is converted into sesquioxide by means of nitric acid; and for this purpose, on that occasion, the College direct pure nitric acid of sp. gr. 1.5 to be employed, while in Ferrugo, they order commercial nitric acid of sp. gr. 1.380 to be used for a similar purpose; for this diversity of practice we can discover no reason; the commercial acid is the more economical, and why it should not have been used in both preparations, we are at a loss to conjecture.

We attempted to prepare this medicine in the mode ordered, adding the nitric acid a fluidrachm at a time to the solution of sulphate of iron, and heating it after each addition; we found, however, on employing the test recommended by the College, of the colour of the precipitate yielded by ammonia, that the whole of the protoxide of iron was not converted into sesquioxide until the boiling had been so long continued as that scarcely 16 fluidounces of Solution remained, consequently 24 fluidounces of water were evaporated; as the solution was evidently much too concentrated to be conveniently decomposed, water was added to it to make it up to two pints, or the original measure; on mixing ammonia with a small portion of this diluted solution in a test tube, so gelatinous a precipitate of sesquioxide of iron was formed, that on inverting the tube scarcely a drop of liquid left it.

The quantity of the solution was then, by the addition of water, increased to four pints, and even then the precipitate given by the ammonia was so bulky, that scarcely two pints of clear liquor could be poured off from it, after allowing eighteen hours for the subsidence of the oxide of iron.

It is we think, quite evident, that if any one had attempted to prepare Ferrugo according to the directions of the Pharmacopoeia they never would have found a place in it; as to the employment of the stronger instead of the weaker solution of ammonia, we refer to what we have said under the head of Ferri oxidum nigrum.

There are some inconsistencies in the College directions for preparing the three precipitated oxides of iron, which we shall point out. Under Ferri oxidum nigrum the ammonia is to be "immediately" added in a full stream to the mixed and hot solutions of protoxide and peroxide of iron, whereas in Ferrugo the solution of iron, with evident propriety, is directed to be allowed to cool, before admixture with the ammonia.

With respect to the Ferri Oxidum nigrum, the precipitate is directed to be washed,"till the water is scarcely precipitated by solution of nitrate of baryta ;" and the precipitated Ferri oxidum rubrum is to be washed "till the water is but litle affected with solution of nitrate of baryta ;" whereas,

Ferrugo is to be waslied "till the washings cease to precipitate with nitrate of baryta." We need hardly say that, in our opinion, the directions in the last case are unreasonable, for we found that less than 10 drachms of Ferrugo required about four gallons of distilled water to effect the purpose directed.

Dr. Thomson, like Dr. Christison, has given fluidounces of sulphuric acid in the formula for Ferrugo instead of fluidrachms, and we should suppose that the former had copied the error from the latter, had we not observed the proneness of Dr. Thomson to commit errors of this sort, as shown by his substituting fluidounces for fluidrachms of nitric acid in the formula for Ferri oxidum nigrum. The directing of fluidounces instead of fluidrachms of sulphuric acid in Ferrugo is not, however, the only grave error which Dr. Thomson has committed in this formula, for he has entirely omitted the nitric acid, so essential to the process; so that we have eight times the proper quantity of one acid directed to be used, and, as if by way of compensation, the whole quantity of another is omitted.

Alluding to this preparation, Dr. Thomson says, "the salt thus formed has a yellowish-brown colour," meaning, we presume, the oxide thus formed; and he further states, "its composition, most probably, when properly prepared, is one part of sesquioxide of iron 80 + 2 parts of water 18, making the equiv. 98 (Fe2. O'. + 2 H. O.)."

=

=

Now, how "one part" can be considered as 80, “or 2 parts" as = 18, we are at a loss to conjecture, and therefore propose to read one equivalent for one part, and two equivalents for two parts; in the formula, O' is misstated for O3.

Ferri Sulphas.-The Edinburgh formula for this salt is entirely left out of Dr. Christison's Dispensatory; it is as follows in the Pharmacopoeia : "FERRI SULPHAS.

If the Sulphate of iron of commerce be not in transparent green crystals, without efflorescence, dissolve it in its own weight of boiling water acidulated with a little sulphuric acid; filter; and set the solution aside to crystallize. Preserve the crystals in well-closed bottles."

Supposing commercial sulphate of iron to contain, as it usually does, some sesquipersulphate, it would dissolve in water, and any subsalt of the peroxide would be dissolved by the sulphuric acid; this process seems therefore calculated to reproduce the impurity which it is intended to remove; whereas, by adding a little iron, the sesquioxide would be reduced to protoxide, and any copper which the commercial salt might contain would be precipitated by it.

Among the formulas for ascertaining the requisite purity of the more important articles and their freedom from known adulterations," we find, with respect to sulphate of iron, the following in Dr. Christison's Dispensatory: "TESTS. Edin. Entirely soluble its solution precipitated by excess of ammonia, yields on filtration a fluid which is colourless or very pale blue."

:

The reader will perhaps scarcely believe that not one word of this statement of the tests is to be found in the Edinburgh Pharmacopoeia, yet such is the case, for the tests which it gives are merely the following. "Pale

bluish-green crystals, with little or no efflorescence." The question then naturally arises, what could induce Dr. Christison to omit the tests of the Pharmacopoeia and make this unauthorised substitution for them? To this inquiry we can imagine that only one answer can be given, which is this: -that whereas Dr. Christison has nearly thirty times objected to the tests of the London College, that they are mere proofs of the nature of the substances and not of their purity, it would hardly be consistent in him to suffer a mere statement of colour, and absence of efflorescence to appear in his Dispensatory as proofs of chemical purity.

But this is not all: it appears from Dr. Christison's representation of the Pharmacopoeia test, that a pale blue colour, occasioned by the action of excess of ammonia, is a test of purity, whereas it is well known to indicate the presence of copper.

Still further: Dr. Christison observes, that "in stating in the Edinburgh formula the ammoniacal test for indicating copper, the preliminary step for converting the oxide of iron into sesquioxide, which is quite essential, has not been mentioned." This observation is made up of candour and unfairness; of candour, because the error is unquestionable and clearly his own; of unfairness, because he attributes it to the College, which, as we have already shown, does not employ this test at all.

When ammonia is added in excess to a solution of protosulphate of iron, the filtered solution becomes turbid by the deposition of peroxide of iron which had been dissolved as protoxide, and attracted oxygen from the air; hence the necessity, as mentioned by Dr. Christison, for converting the protosulphate into persulphate of iron, previously to adding the ammonia.

With respect to the composition of sulphate of iron, we may remark that Dr. Christison has committed several errors; he says:-" The salt is composed of one equivalent of protoxide of iron, one equivalent of sulphuric acid, and six equivalents of water (SO3 + Fe O+ 6 HO), and consequently of 36 parts of base, 40.1 of acid, and 54 of water. Hence the anhydrous salt of the Edinburgh Pharmacopoeia contains about fourfifths more of real sulphate than the crystallised; which must be attended to in prescribing it. As five of the equivalents of water are easily expelled by heat, while a much higher heat is necessary to drive off the fifth, this equivalent is considered by Professor Graham to exist in the salt as a base, so that the constitution of sulphate of iron, according to his view, is SO3 FeO HO+ 5 Aq."

Now Graham's statement does not resemble the above either in form or in fact; his formula (Elements, p. 558) is Fe O, SO3, HO+ 6 HO, showing that it contains not 6, but 7 equivalents of water; if, as stated, the ferri sulphas exsiccatum were anhydrous, (which it is not), then, even admitting the fact, it would be incorrect to assert that it contains any proportion whatever of itself, and yet Dr. Christison says, that "the anhydrous salt of the Edinburgh Pharmacopoeia contains about four-fifths more real sulphate than the crystallized." Now, as 139 of the crystallized salt contain 76 of anhydrous sulphate of iron, 100 will give rather less than 55, instead of 80, as stated by Dr. Christison.

In the above quotation Dr. Christison has mentioned that a higher heat is required to drive off the fifth equivalent of water; this is a mis-print for the sixth; but even when thus amended the fact is not correctly stated;