Notes and Correspondence

In consequence of the difficulty of making the thin glass cells now in use, they are not so frequently employed by microscopists as they would be if their manufacture were more simple, and they could be obtained at less cost. One method of making these thin cells consists in grinding down a thick section of glass tube, or thick glass bottle, until the requisite tenuity has been obtained. This process is obviously quite as laborious as that of drilling through several squares of the thin glass cemented together by marine glue, and afterwards separating them for mounting on the glass slide. By either of these processes it is obviously difficult to obtain cells varying much in size, the usual dimensions of the cell being not more than half an inch in diameter ; and it is almost impossible to make large shallow glass cells by either of the above-mentioned methods. .

Some time ago a very simple method of perforating the thin glass occurred to me, which has been found to answer exceedingly well, and it has this great advantage, that the microscopist can make cells for himself of almost any dimensions required.

The principle of the process depends upon the fact that a crack will not extend across any part of a piece of thin glass which is fixed by marine glue to any firm surface to which it is capable of adhering. The edges of the thin glass may be broken in all directions, but the crack will extend only up to the marine glue, and no farther. If a piece of thin glass be fixed by marine glue to one of the thick sections of tube used for making cells in which injections are mounted, and allowed to cool, a hole may be made in the centre with a file, which may then be carried round the edges, and a thin glass cell exactly the size of the thick one is produced. It is removed by heating the glass, and may then be transferred to a slide and fixed at once, or the glue adhering to it can easily be removed by soaking it for a short time in potash. The surfaces may be roughened, or the cell may be ground thinner by rubbing it on a flat surface with emery-powder in the usual way.

All that is requisite, then, to make thin glass cells of any required form and dimensions, is to obtain a perfectly flat, thick ring, to which the glass may be cemented, and in a few minutes several thin cells of large size may be made, and at very trifling cost.

It may not be out of place here to describe a very simple method of cutting the circular glass covers for thin glass cells. For this purpose several beautiful forms of apparatus have been devised ; amongst others may be mentioned that of Mr. Darker, by aid of which circles of any diameter may easily be cut. A very simple form of apparatus may be made by soldering on each side of several common brass curtain-rings a straight piece of of wire, as in the figure, by means of which the ring can be held firmly by two fingers against the thin glass lying on a perfectly flat surface. The writing diamond is then earned round the inside of the ring, and the circular piece of glass is readily obtained. The rings may be purchased of any size, and by a little bending they may be formed into a very good oval for cutting thin glass of this form.

The usual plan of constructing the deep glass cells, by joining together several slips of thick plate glass, the edges of which have been ground perfectly flat, and cementing them at the angles with marine glue, is a process of considerable labour. For some time past I have been endeavouring to devise a method by which these cells could be more readily made, as their advantage over bottles for mounting many preparations is obviously great. The process about to be detailed requires some practice, but, when this is acquired, cells may be made much more rapidly than by the old method, and have the advantage of possessing fewer joins.

A slip of plate glass, of the required depth, of about the eighth of an inch in thickness, and of sufficient length to make all four sides of the cell, is taken. The length of each side is to be accurately marked upon it with a spot of ink, and in these situations the glass is to be carefully and very gradually raised to a red heat in the blow-pipe flame, and then bent so as to form a good angle ; care being taken not to twist the glass in the slightest degree. The other angles are formed in the same manner, each being cooled as gradually as it was heated. The ends are to be afterwards cemented together by heating in the blow-pipe. If the last side when bent round should be found to be too long, a small portion can be cut off by aid of the .diamond, and, with a little care in heating the ends and pressing the glass together when in a softened state by a small piece of wire, an excellent juncture may be made ; or, if preferred, the join may be effected in the centre of one of the sides. In this way cells may be made of half an inch in depth, or rather more, and of any required size. The great difficulty in constructing cells in this way arises from the glass cracking in the process of heating or cooling, and from the tendency of the sides to twist when the glass is softened in the position of the angles. The latter difficulty is soon overcome by practice ; the former would be avoided if, instead of the ordinary plate glass, flattened and well-annealed flint glass were employed ; and I believe that, with this modification, the construction of cells would be much simplified, and they might be made at a cost far less than that for which built glass cells can now be obtained. When the angles are formed and the glass joined, the surfaces are ground flat in the usual way ; and if care be taken to prevent twisting, this part of the process is soon executed. After grinding they are fixed to a flat plate-glass slab with marine glue. I have succeeded in making several cells in this manner which have now had preparations in them for upwards of two years.—Lionel S. Beale, M.B.—27, Carey Street, Aug. 1852.

The petal of the Geranium is one of the most common and beautiful objects in microscopic cabinets. The usual way of preparing it is by immersing the leaf in sulphuric ether for a few seconds, allowing the fluid to evaporate, and then putting it up dry. Another is by simply drying the petal, immersing for an hour or two in spirits of turpentine, and then putting it up in new Canada balsam.

By neither of these plans is the true structure shown; we can recognise the mamillary process of each cell, but not the few hairs which surround their margin.

The only way in which I have succeeded in preserving these is the following:—I first peel off the epidermis from the petal, which may readily be done by making an incision through it at the proximal end of the leaf, and then tearing it forwards by the forceps. This is then arranged on a slip of glass, and allowed to dry ; when dry, it adheres to the glass ; place on it a little Canada balsam diluted with turpentine, and boil it for an instant over a spirit-lamp ; this blisters it, but does not remove the colour. Cover then with a thin slip to preserve it. On examination many cells will be found showing the mammilla very distinctly and the score of hairs surrounding its base, each being slightly curved and pointing towards the apex of the mammilla. It is these hairs and the mammilla which give the velvetty appearance to the petal.—Thomas Inman, M.D. Liverpool.

Bothrenchyma forms a very popular microscopic object. It is interesting to examine the way in which it may be formed. It may be produced, as in rhubarb, by the filling up of interspaces between fibres until a small pit only remains : or, as in the Alnus serratula, by a number of lines, arranged at first like those of a ladder, then united by transverse ones forming a grating, the angles being filled up and rounded last : or, as in the Populus tremuloid.es, by an uniform deposit over the whole membrane. It is generally known that bothrenchyma does not exist in coniferous wood, but in some varieties a dotted tissue may be distinctly made out, situated in the medullary rays. The wood in which I have found it is that of which eau de Cologne boxes are made. Its rudiments are to be found in common deal. The formation is readily accounted for. Wherever the two sets of fibres or cells cross each other, their angles are filled up, and they form apparently a grating of round holes instead of square. They could never be mistaken for genuine bothrenchyma.

I have heard many suggestions as to the use or intention of these little pits ; passing by the obvious one of their promoting the easy transmission of fluid, the following seems the most striking. They are intended to unite the utmost possible strength with the utmost possible lightness—e. g., if an engineer wanted to cast a pillar which should combine these two qualities, he would mould it on a plan precisely similar to a dotted duct.—Ibid.

Dr. Herapath, of Bristol, has recently described a salt of quinine, which has remarkable polarizing properties. The salt was first accidentally observed by Mr. Phelps, a pupil of Dr. Herapath’s, in a bottle which contained a solution of disulphate of quinine. The salt is best formed by dissolving disulphate of quinine in concentrated acetic acid, then warming the solution, and dropping into it carefully, and by small quantities at a time, a spirituous solution of iodine. On placing this mixture aside for some hours, brilliant plates of the new salt will be formed. The crystals of this salt, when examined by reflected light, have a brilliant emerald green colour, with almost a metallic lustre ; they appear like portions of the elytra of cantharides, and are also very similar to murexide in appearance. When examined by transmitted light they scarcely possess any colour—there is only a slightly olivegreen tinge ; but if two crystals, crossing at right angles, be examined, the spot where they intersect appears as black as midnight, even if the crystals are not l-500th of an inch in thickness. If the light be in the slightest degree polarized— as by reflection from a cloud, or by the blue sky, or from the glass surface of the mirror of the microscope placed at the polarising angle 56° 45′—these little prisms immediately assume complementary colours : one appears green, and the other pink, and the part at which they cross is a chocolate or deep chestnut brown, instead of black. As the result of a series of very elaborate experiments, Dr. Herapath finds that this salt possesses the properties of tourmaline in a very exalted degree, as well as of a plate of selenite, so that it combines the properties of polarizing a ray and also of depolarizing it. Dr. Herapath states, in his last communication to the ‘Pharmaceutical Journal’ on this subject, that he has succeeded in making an artificial tourmaline large enough to surmount the eye-piece of the microscope, so that all experiments with those crystals upon polarized light may be made without the tourmaline or Nicholls prism. He says that the brilliancy of the colours is much more intense with the artificial crystals than when employing the natural tourmaline. As an analyser above the eye-piece, it offers some advantages over the Nicholls prism in the same position, as it gives a perfectly uniform tint of colour over a much more extensive field than can be had with the prism.

Attention has recently been called to the value of the microscope in diseases of the kidney. It has frequently been appealed to in diseases of the lungs, but with less success. My intention is to show that in some rare cases some similarity may be found microscopically between the one and the other.

Dr. G. Johnson has pointed out how constantly one form of inflammation of the kidney shows itself by epithelial desquamation, and how generally the casts of the urinary tubes so produced may be found in the urine.

I have on one occasion discovered the traces of a similar process in the lungs. A friend forwarded me some expectoration from a patient, with a request that I would examine it, and give an opinion, if I could, whether the case was one of phthisis or bronchitis, a question her attendants were unable to solve. As the examination was somewhat instructive, I will give its detail. The first specimen I examined contained abundance of pus and mucous granules, a number of oil globules, and some scattered particles of starch. There was also a fragment or two of fibrous tissue, which might or might, not be a portion of broken-down lung. 1 soon succeeded in obtaining larger specimens of this, and found it was a cellstructure too regular for any in the animal world. By charring, it gave a vegetable smell, and reminded me of burnt bread. I then procured some bran, and found that it resembled it closely. The first diagnosis was then, that the patient had been eating bread and butter. I next took some of the sputa and agitated them with water for a considerable time, boiling at last to dissolve the mucus completely. After a time a white sediment appeared at the bottom of the vessel, consisting of very minute granular particles. These, when examined under the microscope, were found to be accumulations of epithelial cells, arranged in a hollow globular form, and measuring about l-5OOth of an inch in diameter. Most of them were single, and had a small entrance tunnel sometimes opening into a fragment of a larger tube. They resembled very closely a roughly-cast bullet before it has been trimmed. Here and there others were found in small masses, like a diminutive bunch of grapes. The rest of the deposit was made up of amorphous granular membrane, and seemed as if it had come from a large cavity. I considered that the evidence was scarcely sufficient to enable any decided opinion to be given ; for it was not absolutely certain (however probable it was) that these casts of cells came from the lungs, and, if they did, whether they indicated simple inflammation or tubercular disease. The woman suffered much from relaxation of the soft palate, and the cells might be from its mucous glands.

The patient died shortly after, and no examination was allowed.

The results of this case induced me to examine others of confirmed phthisis, but in one instance only have I been able to find a similar appearance. The most common phenomenon is that of a brownish amorphous membrane, of variable size and shape, studded with oil globules and small nuclei, and which seems to be the secretion from a diseased surface, and analogous in a small degree with the amorphous casts found in chronic desquamative nephritis. As these membraniform bodies evidently come from large cavities, and have not been found in those specimens of simple bronchitis that I have examined, their occurrence in the sputa may probably form a diagnostic sign between it and phthisis. My observations have not as yet been sufficiently extended to enable me to declare positively that they are diagnostic. I would only add, as a sort of apology for my first diagnosis, the following anecdote :—A microscopic friend, while examining the sputa of a phthisical patient, detected in it a number of muscular fibres exhibiting the striæ more beautifully than in any preparation he had ever seen. After a long consideration of the case and consultation with another, he came to the conclusion that there was ulceration of some parts of the larynx with loss of muscular substance. It was not for some time after that he ascertained that the sputa were taken after dinner, that the patient had had meat, and that the fibres were due to a slaughtered ox, and not to a human larynx.—T. Inman, M.D. Liverpool.

In the examination of waters supplied by nature for dietetical and economical purposes, a chemical examination of their contents has been usually deemed sufficient in order to ascertain their qualities. It is, however, evident that, however accurately chemistry might be able to pronounce on the quantity of the organic contents of waters, the qualities of these matters can only be ascertained by means of the Microscope. We are indebted to Dr. Hassall for first taking up this subject ; and during the last Session of Parliament Dr. Lankester and Dr. Redfern were examined before the Committee of the House of Commons, on the water supply of the Metropolis, with reference to the Microscopic contents of the Thames and other waters. A report has been drawn up by these gentlemen at the request of the London (Watford) Spring Water Company, in which they give the results of their examination of waters supplied from the Thames, the New River, the Surrey Sand Springs, the river Dee, and water from wells at Watford. The mode of proceeding was, to take half a gallon of the water to be examined, and, after allowing it to stand for a few hours, to decant the clear liquid from above till about half an ounce remained. A drop of this was taken up by a pipette and examined under the Microscope. It would appear from these reports that, in proportion to the absence of inorganic and organic matters in a state of decomposition, is the water free from microscopic plants and animals. Great differences in these respects are presented by the water examined. Thus, in the river Dee and the Watford water, scarcely a living organism was found, whilst in the Thames and New River waters above seventy species have been identified by the reporters.