I* 



MICROSCOPE, USES OP THE. 



MICROSCOPE, USES OF THE. 



18. 



10. A tolerably strong solution of muriate of lime (on* part of dry 

 muriate of lime, and three part* of diitilled water) for preserving 

 microscopic object*. Thia it useful for moat tiling*, even for delicate 

 object*, unlem they contain lUroh. If it is wished to praaenre an 

 object for a few <Uy without mounting it immediately, it u a very 

 good plan to put a drop of thii tolation upon the object, and to place 

 it under a bell-glaw for protection against dint 



11. Glycerine. This is also well adapted for preserving microscopic 

 object*, and especially for celU which contain starch, which latter 

 substance continue* unchanged by it. In granules which exhibit 

 lamination, for instance in the potato starch, the lamination U apt to 

 continue invisible for the first few hoars ; after 24 hours, however, it 

 appears more clearly. 



1 2. Copal Tarnisb, or Canada balsam, also for the preparation of 

 microscopic object* ; these are only to be recommended for a few thin 

 section* of wood, such a* fossil woods. They both make the object 



transparent than the solution of muriate of lime. 

 A tolerably strong solution of carbonate of soda for digesting 

 peat-wood, as well as hydrochloric acid for digesting fossil woods 

 which have been converted into carbonate of lime. It is also recom- 

 mended for examining the sweat-ducts in the skin. 



14. Acetic acid. This is very useful in examining animal tissues. 

 It has the power of making the cell-wall clearer, whilst the nucleus 

 becomes darker and more distinct It also distinguishes phosphate 

 or carbonate of lime from oxalato of lime, by dissolving the two 

 former, whilst it has no action on the latter. 



15. Very dilute chromic acid. It is used for the purposes of harden- 

 ing tissues. It is especially useful in examining the structure of 

 the retina. 



16. Ammonia will be found useful in the same canes where caustic 

 potash and soda are employed. 



17. Nitrate of baryta is used as a tot for sulphuric and phosphoric 

 acids. Sulphate of baryta is insoluble in acids and alkalies, while 

 phonphate of baryta U readily soluble in acids, but insoluble in 

 ammonia. 



18. Nitrate of silver in solution is used as a test for chlorides and 

 phosphates. The white chloride of silver is soluble in ammonia, but 

 insoluble in nitric acid. The yellow phosphate of silver is soluble in 

 excess of ammonia and nitric acid. 



19. Oxalate of ammonia is employed as a test for lime, an insoluble 

 oxalate being formed wherever lime is present 



This list of re-agenta might be increased, as there is scarcely an 

 operation performed in the laboratory that may not be repeated on a 

 small scale under the microscope. The above list, however, comprises 

 those which will be found most useful 



In addition to the ordinary optical arrangements of the microscope, 

 certain forms of accessory apparatus will be found very useful. Some 

 of these have been already alluded to, and the following will also be 

 found convenient 



1 . A spirit lamp, which may be made of brass, tin, or gloss, fitted 

 with a ground glass cap. It may be fitted with a stand, and will be 

 found useful for submitting objects to heat The objection to the 

 employment of candles, or lamps, is the black smoke they produce. 



2. A small warm bath. This will be found of use for drying objects 

 previous to being mounted in Canada balsam. 



3. Watch-glasses are useful for examining substances in fluids with 

 low powers, as by this means a considerable depth of fluid is obtained 

 for observation. 



4. Plate-glass slides, 3 inches long and 1 inch broad, are useful for 

 mounting and examining all kinds of bodies. 



5. Thin-glass, called cylinder-glass, of different degrees of thick- 

 ness, U indispensable for placing over object*, especially those which 

 are soft or fluid when placed upon a slide. 



0. Needles of various sixes are used for making minute dissections. 

 Small handle* may be attached to them, rendering them more easy to 

 work. Needles or pins may be employed for fastening down minute 

 organic bodies which are about to be submitted to dissection. 



7. Scissors of various sizes will be found serviceable. These may 

 be obtained of the surgeon's instrument makers. 



8. Knives, scalpels, and razors, for cutting soft or hard object*, should 

 be kept at hand. 



9. A pair of thin brass forceps will be found convenient for placing 

 thin glass on the slides, as well as for placing or removing object* 

 from the slide*. 



10. A guts-cutter's diamond is useful for cutting slips of glass, in 

 the making of cells, and in writing the names of preserved object* 

 on the glass slide*. 



Cement* of various kinds are necessary to the microscopic observer 

 who wishes to preserve the object* he examine*. They are used 

 for making glas* cells to contain objects, on the glass slide, and for 

 fixing the cover after the preparation has been placed in the cell, and 

 for other purpose*. The principal cement* used are gold-size, sealing- 

 wax varnish, solution of shell-lac, gum, a French cement composed of 

 lime and Indian-rubber, Brunswick-black, marine-glue, acd Canada 

 balsam. These cement* are most' of them sold at the optician's 

 and directions for making them are found in some books on chemistry 

 and the microscope. 



In order to preserve preparations for a length of time it U neces- 



sary to place them in an air-tight vessel. These vewols are c tiled cells 

 and are best made of glass. They are also sold where microscopes are 

 procured. With a little practice however the microsoopUt may make 

 Lis own cells. 



Thin cells may be made of various substances. Even paper answers 

 exceedingly well in some cases, and is well adapted for dry prepara- 

 tions. A thin layer of white INK!, which has been allowed to dry, 

 has also been employed for the same purpose. White lead, made into 

 a thick liquid with linseed-oil aud turpentine, has been recommended 

 by some observers. Various varnUhes have likewise been used ; but 

 where it is required to keep the specimen in some preservative solution 

 glass is the substance which in all cases forms the best material for 

 making cells. 



Sometimes preparations are of such extreme tenuity that it is only 

 necessary to place them on the slide with a drop of some preservative 

 solution, and then to cover them with a square of thin glass, the edges 

 of which have been anointed with gold size or other appropriate 

 cement The superfluous fluid is next absorbed with bibulous paper, 

 and the slide allowed to dry for a few miuutes. A layer of gold-size 

 or other cement is then applied round the edges of the thin glass in 

 order to fix it to the slide. In this way an excessively thin cell may 

 be formed ; but preparations mounted in cells made in this manner 

 can seldom be kept for any length of time without the entrance of 

 nir-bubbles. This arises from the outer layers of the gold-size drying 

 more rapidly than the more internal layers. By the contraction thus 

 produced the edges of the cement are drawn off from the glass, to 

 which however it doe* not adhere with great tenacity in consequence 

 of the surface being highly polished. It is therefore always better to 

 make very thin cells of glass or other material, which can be cemented 

 to the glass slides with marine glue or other cement ; or else to make 

 the cell by painting the slide with a ring of varnish, marine glue, or 

 Brunswick black, and allowing this to dry thoroughly before the 

 preparation is placed in it. In this manner the thinnest cell* which 

 can be required are readily made. 



Perhaps Brunswick black is, for the purpose just mentioned, the 

 best It is painted upon a glass glide with a fine camel's-hair brush, 

 and allowed to dry perfectly, when, if the cell is not sufficiently thick, 

 another layer may be applied. If the cell be required immediately, it 

 is better to warm the slide slightly before applying the varnish. If 

 too great a degree of heat however be employed the varnish become* 

 brittle and the cell unfit for use. 



Very thin cells may be made of tin-foil. This may be easily accom- 

 plished by cutting with a pair of scissors a piece of thin tin-foil the 

 size of the cell which it is desired to make. A hole is cut in the 

 centra of the tin-foil sufficiently large to hold the preparation which 

 is to be preserved, and the tin-foil is then attached to the glass slide 

 with marine glue. When culd the cell may be filed perfectly flat 

 with a very fine file, or rubbed with a little emery upon a piece of 

 plate glass, and the marine glue should be afterwards removed from 

 the centre with a little solution of potash. The cover may be fixed 

 on with gold-size or varnish, as in other cases. Thin cells have also 

 been made of gutta percha, but there is great difficulty in fixing the 

 cell firmly upon the glass slide. This however has been effected by 

 some observers ; but in consequence of the difficulty it is a method 

 not generally employed. Preparations however mounted in cells 

 composed entirely of gutta percha keep very well for a length of time. 



CelU composed of very thin glass are perhaps the most convenient, 

 and will be found useful for preserving many preparations. They 

 may be obtained of different degrees of thickness, and are made 

 usually by perforating the thin cylinder glass which is used for 

 covering the cells, or by grinding sections of a thick glass bottle to the 

 required tenuity. Hound cells of thin glass are made as follows : A 

 great number of squares of thin glass are cemented firmly together 

 with marine glue, and when cold a hole of the required size U drilled 

 through them all They are next separated from each other by heat, 

 and, after being cleaned with potash, may be fixed on the glass slide* 

 with marine glue in the usual way and kept ready for use. It is a 

 good plan to roughen the surface of these cells, which renders the 

 subsequent entry of air less likely, as the gold-size adheres much more 

 firmly to a ground than to a polished surface. ThU is readily effected 

 by rubbing the cell, after it has been fixed upon the glass slide, up and 

 down a narrow hone or strip of plate glass on which some moistened 

 emery powder hag been placed. In this way also the thickness of the 

 cell may be reduced if required. (Beale.) 



Cells of any thickness or depth may be made for larger objects, but 

 those described will be found most convenient. 



If it is only required to examine the character of a specimen in a 

 dry state, it may simply be laid upon a glass slide and placed iu the 

 field of the microscope ; if however the substance be of a very delicate 

 structure, or in a minute state of division, it U better to place a piece 

 of thin glass over it in the usual manner in order to protect it. 



Dry object* may be mounted in a thin glass cell, or in a paper cell, 

 or if of extreme tenuity they may simply be placed on a glass slide 

 and covered with thin glass, which should be fixed to the former by a 

 small piece of gummed paper (rather larger than the glass cover), in 

 the centre of which a hole has been cut of sufficient size to permit 

 the entire object being seen. The paper may of course be of any 

 colour, or ornamented according to the taste of the operator. 



