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The appearance which first presents itself is that of minute projections of one solution into the other, accompanied at the line of contact by Fig. 2.

a faint pebulosity, evidently arising from the particles of carbonate of lime there formed being then too minute to admit of being distinguished individually. (See Fig. 1, a.) In a short time—about an hour-portions of the nebulous part disappear, and are replaced by minute spherules, still too small to admit of accurate measurement. These are produced by the coalescence of the molecules which had before constituted the nebulosity. (See Fig. 1, b.) Next, these spherules, becoming fused together, form

larger ones, which, in attaining an exactly spherical figure, pass through various intermediate forms, such as that of dumb-bells, caused by the contact of only two sphernles, and ellipses of different degrees of eccentricity. (See Fig. 1, c. and d.)

To examine the larger FIG. 3.

and more perfect forms of this compound, some deposit, taken from solutions which had stood for about a month, should be obtained, which, after being dried, must be put up in Canada balsam. Figs. 2, 3, and 4 contain representations of all these forms, which will be more particularly referred to when the manner in which they are severally produced, and the physical forces upon which their production depends, come under consideration. For this purpose the accompanying figures will serve, better than any verbal description, to convey an accurate idea of the appearances indicative of

the different stages of coalescence; and as it will be more easy to refer to them than to written descriptions, I shall at once proceed to consider the cause of these appearances, and the manner in which this cause acts in producing them.

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a

As every particle of matter, whatever may be its size, is under the influence of a force called gravity, to which the molecules of carbonate of lime, as produced in the manner already described, can form no exception, it will follow that the instant they are brought into existence they will commence arranging themselves in spherical figures, unless there should be some other force of an opposite kind acting upon them, either adequate entirely to overcome that of gravity, or sufficient only imperfectly to oppose its influence, in which case results of an intermediate kind would be produced, depending upon the relative powers of the opposing agencies. Now as it is a fact that the molecules of carbonate of lime, when formed in a solution of vegetable gum or albumen of the same specific gravity as the molecules themselves, do become arranged in spheres, the force acting upon them, and thus causing them to assume the spherical form—that is, to take up such a position one with respect to the other as to bring

FIG. 4. the greatest number of molecules into the smallest possible space-must either be universal attraction, or some other force capable of acting upon the particles of matter precisely in the same manner. Now as the latter supposition is not likely to be true, the spherical form of the first set of particles of the carbonate of lime, formed under the circumstances detailed in the experiment, can be attributed only to gravity.

The formation of the smallest, or first set of spherules, that is, of those only just sufficiently large to present an appreciable form under the highest magnifying powers, being considered, it next remains to offer a few remarks on the manner in which these coalesce to produce larger ones. Now, as it has been demonstrated by Newton, that in a sphere the total attraction resulting from the particular attractions of all its component atoms is the same with respect to any body drawn towards it, as if all the attracting particles had been concentrated at the centre, these minute spherical particles, as so many gravitating points, will be drawn towards each other with a force varying inversely as the squares of the distances between their respective centres; hence, being contained in a medium of the same density in which external sources of attraction will be balanced, it is evident that they will by their mutual attraction alone readily form themselves into spherical masses. Now, as each of the spherical particles entering into the composition of these masses can only maintain its spherical form so long as all its component molecules are balanced between equal and opposite attracting forces, it must follow that when these spherules are brought into apposition with others of the same kind, as in the above con

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glomerations, the balance in each will be destroyed; and that the molecules, which were before at perfect rest, will now be thrown into a state of molecular agitation; and, as it is admitted, and that upon the best grounds, that the atoms composing all bodies, whatever may be their degree of hardness, are not in the condition of absolute contact, but are so circumstanced as to allow of a limited extent of motion among themselves, there will be no difficulty in comprehending how the same attractive force which had been at first separately exerted upon the molecules of individual spherules, so as to dispose them in spherical figures, will suffice, when exerted upon those of several spherules at the same time, to arrange them also in one aggregate spherical mass. Now as all the molecules of every component spherule had been before arranged in reference to its own centre, the position which these molecules will have to take up in the new sphere will differ from that which they before occupied in the old spherule; and as the sum of the spaces occupied by the component spherules must exceed that of the space which they will fill up when they are all incorporated into one sphere, it being the property of spheres to present a maximum of capacity with a minimum of superficies, it will follow as a natural consequence that each molecule, after leaving its component spherule, will have to pass over a certain space before it can obtain a fixed position in the sphere of which it is about to form a part. Hence, prior to the complete coalescence just mentioned, all the molecules of the component spherules must undergo a process of complete disintegration before they can attain that condition of perfect stasis which results from each molecule being balanced between equal and opposite attractive forces. See Fig. 3, e, which represents the sections of two calculi of equal size placed in apposition; also the section of one which would be produced by their union, whose proper situation and relative size is constructed in accordance with the fact of the capacities of spheres being as the cubes of their radi, and the correctness of the above deductions will be obvious.

The two molecules at the point of contact being between equal and opposite forces, will be as if not attracted at all by either sphere, but only by one another, and therefore being in this way detached each from its former sphere, will be in the condition necessary to form the centre of the new sphere; the molecules of the adjacent spheres in the vicinity of this point being only feebly attracted by one another, that attraction being as their distance from it, will be in a condition to admit of easy displacement by the molecules in the remoter hemispheres; which, having their attraction for one another less enfeebled, will be drawn together en masse, and thus the contents of the remotest portions of the two component spheres will be brought inwards into the outer portions of the space representing the section of the resultant sphere, whilst those situated nearer to their centres will be forced in opposite directions, some forwards into the fore part, and others backward into the back part of this same space; until all the molecules of the two spheres continuing thus to enter it, some moving towards its centre, and others from it, will entirely fill up this said

space. Now as the molecules occupying the outer parts of the surface of the two component spheres will, from their position, be the last to reach the line indicating the surface of the aggregate sphere, over which they cannot go, and as those on the portion of the surface of these two spheres contained within the area of the circle intended to represent the section of the resultant sphere will be nearer than the other molecules to its surface, beyond which they cannot pass, it will follow that when the new sphere is completed, its superficies will be made up of a part of the molecules which had before entered into the composition of the superficies of the old spheres. And as the same reasoning will apply to the next and all the subsequent layers of particles, it will be obvious that the greater part of the molecules which had occupied any given position in relation to the centre of each of the component spheres will be similarly placed with respect to the centre of the aggregate sphere.

If the two component spherical calculi should be similarly laminated, as represented in Fig. 4, ā, it will be apparent from the inspection of this figure that at the contiguous extremities of any two laminæ similarly situated in the two coalescing spheres, the molecules of each lamina will be under the same mechanical conditions—that is, they will be equally and oppositely attracted, just as the two molecules were which had united to form the centre, and therefore these will coalesce in the same manner. The same reasoning will apply to all the other molecules similarly situated in the two spheres, until both are blended together into one.

Some large calculi are formed by the coalescence of several small spherules of nearly the same size. The first stage in the formation of such calculi is a spherical conglomeration of these spherules, presenting a mulberry appearance (see Fig. 4,6, c, d), and looking very much like a form of corpuscle called by pathologists a “glomerulus.” This form of calculus furnishes a good example of the process of coalescence, but still not so remarkable as the one just described. The first indication of this process is an indistinctness and want of definition of outline of all the component spherules, especially of those nearest to the surface. These afterwards lose every vestige of their original form, and become converted into an amorphous granular mass, of the form of the original conglomeration. Next, the disintegrated molecules nearest the surface coalescing, form a clear ring completely surrounding the amorphous matter occupying its interior. (See Fig. 4, 6.) As the processes of disintegration and subsequent coalescence progress, the circumferential bright ring increases in width as the central amorphous part diminishes (see Fig. 4, d), until all the latter disappears and is replaced by a succession of bright concentric laminæ, extending from the circumference to the centre, as shown in Fig. 3. Now, the fact of the disintegration of the component spherules and the subsequent coalescence of their disintegrated molecules in bright rings, beginning at the circumference and terminating at the centre of one of these compound calculi, is exactly in accordance with the effect which gravity is well known to exert upon the particles of bodies pro“ 2. Closing the neck of the hernial sac throughout its whole length; and

3. Effecting these changes without injury of the hernial sac, and consequently without risk of peritonitis.” (p. 66.)

The author reviews several of the various circumstances under which the operation may be undertaken, and concludes that it is perfectly admissible “ in most cases of hernia, and that it ought to offer great advantages, especially for patients of the poorer labouring classes.” (p. 94.)

As general contra-indications he would consider: “1. Tender age, partly because at such a time the bloodless treatment by compression is most frequently fully sufficient, partly because the necessary rest and other precautionary measures cannot be enforced with very young children.

“ 2. A very advanced age, because in old persons the wound and long confinement are in themselves always attended with a degree of danger which is not counterbalanced by the diminished necessity for, and scanty prospect of, a radical cure which exist in the case of such patients.

"3. Enormous distension and relaxation of the abdomen, with numerous hernial protrusions of the walls, which are sometimes almost as thin as parchment. This rare and entirely incurable form of hernia, which may also oceur in younger individuals, is especially met with in very old persons who, after having previously been very corpulent, have in advanced years become extremely emaciated; and most particularly in women who, in addition, have in earlier life had many children; this contra-indication hence most frequently coincides with that immediately preceding.

“4. Actual eventration, where the abdominal cavity becomes so contracted around its diminished contents, that the prolapsed viscera have lost their jus domicilii, and no longer find space in the abdomen.

"5 (and lastly). Established specific dyscrasiæ, or profound general cachexy, constitute a decided contra-indication to this as to all other operations.” (p. 94.)

Dr. Mesterton appends an extensive bibliography of his subject, and his volume is illustrated with a plate representing the instrument employed by Gerdy, Zeis, Wutzer, Rothmund, Langenbeck, and Valette. The present essay appears to be intended as the first of a series on the subject of hernia, and is published in a style worthy of what will form, if the succeeding parts shall be equal to that which has already appeared, a classical work on Swedish Medical Literature.

ART. VII.-How to Work with the Microscope. A Course of Lectures

on Microscopical Manipulation and the Practical Application of the Microscope to different Branches of Investigation. Delivered during the Winter Session, 1856–7. By LIONEL S. BEALE, M.B., F.R.S., Licentiate of the Royal College of Physicians, Physician to King's

College Hospital, &c.—London, 1857. Pp. 124. The present generation of microscopic observers enjoys numerous advantages over its predecessors, not only in possessing more perfect tools to work with and more definite aims to accomplish, but also in being able easily to obtain that instruction in manipulation which has caused so much loss of time to those who had to acquire the knowledge for themselves empirically. The lectures of Dr. Beale are

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