Read Ebook: Section-Cutting A Practical Guide to the Preparation and Mounting of Sections for the Microscope Special Prominence Being given to the Subject of Animal Sections by Marsh Sylvester

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Let us consider these conditions somewhat carefully.

If the knife were perfectly rigid, and the curved edge and back lay entirely in the same plane, this difficulty would not occur to any great extent. But since a curved edge rarely lies wholly in the plane of the back of the knife, and since the blades of most knives, especially those thin ones used for cutting sections of soft tissues, yield a little to pressure, and since this pressure is never exactly the same, it is impossible to prevent irregularities from occurring.

While it is not necessary that the back of the knife and the cutting edge should be parallel to each other, it is absolutely necessary that they be in the same plane, or, as mechanics say,--"out of wind." If this condition be not observed, the blade will rock on the microtome table as it passes over it, and irregularity in thickness of section will result.

A slight knowledge of geometry will enable any one to see that these statements are strictly accurate.

As regards other points in the form of the knife, we refer to what has been previously said when discussing the general principles which should govern the construction of cutting tools.

We now proceed to give a few practical directions for sharpening knives and razors and keeping them in order.

Section knives, during the process of sharpening, are subjected to three distinct processes: 1, Grinding; 2, Honing; 3, Stropping.

Grinding is one of the most important, though it is probable that it will rarely be undertaken by the microscopist himself. More knives and razors are spoiled in grinding than in any other way. We have now in our possession an excellent knife, which in an evil hour we entrusted to a New York cutler, and received it back utterly ruined, the temper being entirely taken out of the blades! Some of our readers may wonder at this, but unfortunately it is too true. The cutler, to save time and trouble, too frequently holds the blade against the stone with such force that it becomes over-heated, especially when he is a little careless and allows the supply of water to fall short. The owner does not find this out until he discovers that the knife is ruined, because nothing is more easy than to cool the blade and grind off the tell-tale blue spots. When charged with his rascality, the cutler always denies it and lays the blame on a "soft spot in the steel"--a miserable subterfuge--too transparent to deceive the least experienced.

Footnote 20:

Nothing is more easy than to heat a thin rod or stout wire red hot by holding it against a dry grindstone rapidly revolving. We have often kindled fire in this way.

The only protection against this is either to entrust the knife to a man of known carefulness and integrity, or to stand over him while he does it. If the knife be ground under the owner's eye, no fear need be entertained, because it is easy to insist upon the use of plenty of water.

The grindstone used for section knives should be of fine grain, and it should run true and be very straight across the face, otherwise it will be impossible to grind the knife true, and this, as we have seen, is a necessity.

The surface of the hone must not only be true and smooth, it must also be clean and free from dust and grit, a single particle of which may spoil the work of hours. It should therefore, when not in use, be kept constantly covered. It is always used with oil, and this oil should be of a kind that does not readily dry up. Good sperm is excellent, and so is purified neat's-foot oil. Avoid kerosene, soap and water, and similar fluids, which are so frequently recommended, especially under the guise of new discoveries. They have all been tried and found wanting. After use, the stone should be carefully wiped clean, fresh oil being applied when it is next used. It must never be used without a liberal supply of oil, otherwise it will become glazed and will no longer act on the steel.

This wire edge is a nasty thing when it breaks off on the hone. Unless removed it will very speedily ruin a fine knife, therefore look out for it and wipe off the hone carefully if you have any suspicion that particles of steel have broken off the blade and got on to it.

In honing, as in everything else, however, nothing but practice will impart skill, and he who intends to become an expert should practice on a few old razors, grinding, honing and stropping them himself, until he has acquired the art of giving them an edge far keener than most of the razors ordinarily used for shaving.

Our readers have doubtless seen the "Cheap John" strop-vendors take a rough table knife, strop it on one of their "patent" strops and cut a hair with it. Nevertheless such a knife, sharpened in that way, would not cut good sections, and such a strop is not just the thing for giving the finishing touch to a section-knife, even though the label does say that it is "intended for surgical instruments."

Footnote 21:

The finest emery paper, glued on a strip of wood and used as a strop, will impart to a razor an edge sufficiently keen to enable it to remove the beard, and if paper three or four degrees coarser be used, a very dull knife or razor may be sharpened, and afterwards stropped on the finer emery until it is keen enough to cut a hair. But it will be found that cutting edges produced in this way are not smooth enough for section-cutting.

The best material for a strop is good calf-skin, well tanned, and firmly glued to a strip of wood with the hair side out. The leather should be hard, otherwise it will rapidly round the edge of the knife. The way in which this occurs is readily understood from figures 11 and 12. In Fig. 12 the leather is seen to rise up behind the edge of the blade as the latter passes over it, so that instead of two plane facets meeting at an angle of from 15? to 20? as left from the hone, the edge has become considerably rounded and the ultimate angle of the cutting edge is nearly or quite doubled. The hardest and firmest leather should therefore be chosen, avoiding of course any leather that has been made hard and unpliable by the action of water or other agents. Two sides will be found enough for a strop. On one the leather should be kept clean, while the other should be thoroughly impregnated with fine grained, but very hard rouge or crocus. Rouge is an artificial oxide of iron prepared by exposing sulphate of iron to heat. The hardness of the resulting powder depends upon the temperature to which it has been exposed, and this temperature is very well indicated by the color which the rouge assumes. Bright red or crimson rouge is soft and will not cut steel; hard rouge, suitable for polishing steel, is purple in color, and this quality should therefore be chosen. Great care should be taken to see that it is free from gritty particles, and it should be well rubbed into the leather in a dry state. All mixtures of grease and oil with abrasive substances should be eschewed. If the leather be of good texture and the rouge hard and fine, a very few strokes will suffice to impart the last degree of smoothness and keenness to the blade.

Footnote 22:

Rouge may be purchased from dealers in watch-makers' tools. Those who cannot procure it readily may very easily prepare it for themselves. Full directions may be found in the "Amateur's Handbook." New York: Industrial Publication Company.

Since grit and dust would soon spoil the strop, it should be kept carefully covered and protected. The rouge will require occasional renewing, which may be done by sprinkling a little lightly over the surface and rubbing it in with the finger. Consequently we find that the best and most convenient holder for rouge is a bottle with some fine but porous fabric tied over the mouth of it, forming as it were a sort of dredge. Over the bottle mouth and its cover should be tied a paper cap to keep out dust.

We have thus endeavored to give, in as simple a manner as possible, such information as will guide the microscopist to the acquisition of skill in this most important but generally despised department of his art. We are told by the biographer of Swammerdam that a great deal of his success was to be attributed to his skill in sharpening his fine knives and scissors. The same is also stated of other noted workers, and yet none give even the slightest directions to the novice who desires to follow in their footsteps. There is not to our knowledge a single book in the English language which treats fully of this subject, with perhaps the exception of Holtzapffel's work on "Mechanical Manipulation," and this has long been out of print. As previously stated, however, it is only by practice that the necessary finger-skill can be acquired, but this skill is well worth acquiring at any cost. The man who depends upon cutlers and knife grinders will never make satisfactory progress.

NOTE H.

We are inclined to believe that the difficulty of enclosing glycerine does not arise from the dissolving action of this liquid, so much as from the great adhesiveness which exists between it and glass. Oily cements are of course attacked by glycerine, but shellac and several other gums are insoluble, and drying oils, if well oxidized are also insoluble. Where cells are used they must be first firmly attached to the clean slide, and the cement should also be brought into direct contact with the clean cover. Glycerine does not evaporate at ordinary temperatures, and consequently wherever the slide or cover is soiled with it, no cement will ever adhere until the glycerine has been wiped off. There is no prospect of its drying.

The solution here referred to, and which is known as Kleinenberg's solution, is made in the following way:

Make a saturated solution of crystallized calcium chloride in 70 per cent. alcohol, and add alum to saturation. Make also a saturated solution of alum in 70 per cent. alcohol. Add to in the proportion of 1:8. To the mixture add a few drops of a saturated solution of haematoxylin in absolute alcohol.

This solution may be used in very many cases for staining sections, in place of the ordinary watery solution of logwood alum. It may, if required, be diluted with the mixture of 1 and 2. The stained sections are placed at once in strong spirit.

Acetic acid, 38 Adipose tissue, 63 AEther microtome, 24 Air-bubbles, 40, 55, 62 Alcohol, 17, 19 absolute, 54

Balsam, Canada, 46, 51 to clean from slide, 55 Beale's carmine fluid, 33 Bell's cement, 41 Blue staining fluid, 60 Bone, 16, 57 decalcified, 58 Bottles for media, &c., 48 Brain, 59 Brunswick black, 41

Capillary attraction, 55 Carmine staining, 32 Carpenter, Dr., 37, 41 Cartilage, 60 Cells, to make, 59 Centring slide, 38 Chloroform-balsam, 51, 54 Chromic acid, 17 Clove oil, 51, 54 Coffee berry, 62 Cover, applying, 37 German plan, 39 Crochet-needle holders, 39

Double staining, 73 Dry mounting, 58, 65, 72

Fat, 63 Finishing slide, 54 Fibro-cartilage, 62 Freezing method, 42-47 Fresh tissues, to cut, 15-17 Fruit stones, 58

Gardner, Mr., 25, 31 Gelatine cement, 41 Glycerine, 37, 38 Gold staining, 58 Gum, imbedding in, 22, 66 strong, 43 weak, 31, 71

Ice, for freezing, 43 Injections, to harden, 19 Ink staining, 70 Intestine, 42, 43, 64 Iron staining, 61

Leaves, &c., to cut, 12 Ligaments, intervertebral, 62 Lime, carbonate of, 37 Liver, 65 Logwood staining, 47 Lung, 43, 65

Needles, microscopical, 39

Orange-peel, 67 Ovary, 67

Rangoon oil, 14, 47 Razors, 20, 26, 29, 30 Rush, 78 Rutherford's microtome, 24, 31 "Practical Histology," 43

Taste-bulbs, 71 Teeth, 16, 58 Tongue, 71 Tubes, collapsible, 56

Valentin's knife, 14 Vegetable ivory, 72 tissues, to prepare, 12 Vessels, porcelain, 33

Water-bath, cheap, 29 Whalebone, 64 White zinc cement, 56 Wood, 72

Books and Periodicals

PUBLISHED AND FOR SALE BY

THE INDUSTRIAL PUBLICATION COMPANY,

For the Workshop and the Laboratory. Second Edition. Greatly Enlarged. Neatly Bound 15 cents.

This is a handy little book, containing just the information needed by Amateurs in the Workshop and Laboratory. Directions for making Alloys, Fusible Metals, Cements, Glues, etc.; and for Soldering, Brazing, Lacquering, Bronzing, Staining and Polishing Wood, Tempering Tools, Cutting and Working Glass, Varnishing, Silvering, Gilding, Preparing Skins, etc., etc.

The New Edition contains extended directions for preparing Polishing Powders, Freezing Mixtures, Colored Lights for tableaux, Solutions for rendering ladies' dresses incombustible, etc. There has also been added a very large number of new and valuable receipts.

This is undoubtedly the most thorough treatise extant upon section-cutting in all its details. The American edition has been greatly enlarged by valuable explanatory notes, and also by extended directions, illustrated with engravings, for selecting and sharpening knives and razors.

Intended for those who have absolutely no knowledge of the Microscope or how to use it. Price, in Boards, 30 cents. In Cloth, Gilt Title 50 cents.

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