Microscopist

“ It is not every microscopist that is able to see the minute details of cell-structure lately announced. The careful preparation of material and exceedingly delicate manipulation required need years of practice, and the discoveries referred to are due to the first microscopists of the age, though the methods are now so simplified that any skilled observer, with a good instrument and proper care, may hope to successfully employ them. ”

“ The slides can be procured of any large dealer in optical instruments, or, what is still better, the young microscopist can soon learn to prepare them for himself, as ample directions are given in the books on the microscope. ”

“ There are many other forms of spicules to reward the painstaking microscopist who searches for them, some of them minute and requiring the higher powers of the instrument and careful examination of the lighter washings, but the most beautiful and distinctive are those which we have seen and which can be easily demonstrated with the most ordinary microscope. ”

“ Along with this I purchased every possible accessory,—draw-tubes, micrometers, a camera-lucida, lever-stage, acromatic condensers, white cloud illuminators, prisms, parabolic condensers, polarizing apparatus, forceps, aquatic boxes, fishing-tubes, with a host of other articles, all of which would have been useful in the hands of an experienced microscopist, but, as I afterwards discovered, were not of the slightest present value to me. It takes years of practice to know how to use a complicated microscope. ”

“ They are found in immense quantities, and afford the microscopist innumerable objects. The same treatment as that usually employed for the Diatomaceæ must be followed with these deposits, but as they are sometimes obtained in hard masses, disintegration is first necessary. ”

“ How I longed to discover the secret of some perfect lens, whose magnifying power should be limited only by the resolvability of the object, and which at the same time should be free from spherical and chromatic aberrations—in short, from all the obstacles over which the poor microscopist finds himself continually stumbling! I felt convinced that the simple microscope, composed of a single lens of such vast yet perfect power, was possible of construction. To attempt to bring the compound microscope up to such a pitch would have been commencing at the wrong end ”

“ In testing for poisons the microscope is invaluable. Frequently only the most minute traces of the poison occur in the system and the modern microscopist who makes a study of poisons and their [250] detection can solve mysteries which would have baffled all the scientists in the world in days gone by.
Our chemical studies with the microscope may well begin with various common crystals; they are usually easy to prepare; the process of crystallization is always interesting to watch, and as objects for the microscope it would be difficult to find anything more beautiful than these home-made gems. ”

“ SECTIONS AND HOW TO CUT THEM, WITH SOME REMARKS ON DISSECTION. Many objects are almost worthless to the microscopist until the extraneous matter is removed from them; and this is frequently difficult in the extreme to perform satisfactorily. As an instance, certain Foraminifera may be mentioned in which the cells are placed one upon another, consequently the object must be reduced to a certain degree of thinness before a single uniform layer of these cells can be obtained to show something of the internal arrangements. ”

“ Smaller and eminently suitable for the general worker is “Modern Microscopy,” by Messrs Cross & Cole. Those who wish to specialize in one of the sciences, such as Botany, Zoology, or Geology, will find no lack of books dealing with the subject that most appeals to them. For photographers who are also microscopists, we know of no better books than “Practical Principles of Plain Photomicrography,” by G. West, or the more advanced “Handbook of Photomicrography,” by Messrs Hind & Randles.
Neither books nor teacher will be able to reveal to any of us all the secrets of the microscope. ”

“ It may be taken as an axiom with microscopists that “neither the penetrating power nor the high-power defining objective is alone sufficient for every kind of work. The larger the details of ultimate structure, the narrower the aperture—and the converse; the minuter the dimensions of elementary structure, the wider must be the aperture of the objective.” Every worker with the microscope must have satisfied himself of the truth of this statement, when engaged in the study of the movements of living organisms, or defining the intimate structure of the minuter diatoms, or of the podura scale. ”

“ It is a mistake to suppose that direct light is more critical than indirect. As a rule, the student is given to over-illuminate the object. These questions will, however, be discussed further on.
Very many modifications of Gillett’s condenser have, since 1850, become known to microscopists. Ross’s present improved form (Fig. 127) is made to drop into the sub-stage of the microscope, and when adjusted, is an extremely efficient instrument. The optical part is similar to a 4⁄10-inch objective. ”

“ To derive advantage from the use of the microscope, it is not necessary that one should master all the technicalities of the instrument, or be possessed of all the improved appliances for extremely minute observations. Professional microscopists have recognized the error of directing all one's efforts on such tasks as the resolution of test-plates, so long as really urgent work remains undone. ”

“ The microscopist who relies altogether on the dealer for his permanent preparations may expend a good deal of money, but the satisfaction which he derives from his hobby will be very inferior to that experienced by the worker who endeavours to secure, for exhibition or for reference, specimens of the objects which he finds most interesting and instructive to himself. ”

“ In a great number of hairs there is a quantity of greasy matter106 which must be got rid of by soaking in ether or some other solvent before mounting.
We may next consider the best method of procuring sections of wood, which must be cut of such a degree of thinness as to form transparent objects, and so display all the secrets of their structure. There is no monotony in this study, as the forms are so various, and the arrangement of the cells and woody fibre so different, that the microscopist may find endless amusement or study in it. ”

“ An object which is interesting to the microscopist, as well as the unscientific observer, is the growth of seeds, as it is often erroneously termed. A shaving of the outside of the seed is taken and laid upon the glass slide; a thin glass cover is then placed upon it, and a drop of water applied to the edge of this. The water will then gradually flow under the glass and reach the section of the seed, when the transparent fibres will appear to spring out and “grow” for some minutes. ”

“ As microscopists, we have to fortify ourselves in every way that will sustain, by truthful work, the value of the microscope as a means of research, sometimes conducting our experiments under the most trying circumstances. Fibers may be so treated by experts as to make it difficult to determine how their changed appearance has been effected, and it may happen in this age of experiment and of fraud that important decisions in commercial transactions and in criminal cases may depend on our observations. ”

“ The young microscopist must remember that when he is examining any object by transmitted light, he must arrange it as flatly as possible on the glass. In many cases, a still neater manipulation is required—as, for example, when the petals of flowers are under examination. Thin glass is to be purchased at any optician’s, and if cut in squares, instead of circles, is very much cheaper, and quite as useful for all practical purposes. Lay the petal on the glass plate, place a piece of the thin glass upon it, and press it gently while examining it. ”

“ Even if you should be able to procure a good microscope, get a pocket-lens as well, for you will want them both, and we may say that the most practiced microscopists, and those who are possessors of the most elaborate instruments, are the very men who are the most certain to have a pocket-lens about them, and to use it most frequently. ”

“ The fact that the most skillful microscopists of the age all differ upon the true appearances of a common and not very minute object, and the microscope itself presenting to the vision the most opposite appearances of one and the same object, should act as a caution to those who accept too readily theories based upon microscopical research ”

“ He shows that microscopes of American manufacture possess all the excellences of foreign instruments, plus certain mechanical simplifications the product of American inventive genius.
The "Preparation of Microscopic Objects" has nearly 250 pages devoted to its treatment. This is a very important branch of the technique of microscopy, and the student will find here all the practical directions he needs, derived from the experience of the most eminent microscopists. ”

“ As it is always desirable to examine the gathering on the ground, a “Gairdner’s hand microscope” with powers from 80 to 200 diameters will be found very useful. The best gatherings are those which represent one species abundantly. Those which are mixed may be rejected, unless they are seen to contain something valuable or important, as the object should be not so much to supply microscopical curiosities as to collect material which is available for the study of nature. ”

“ Any object which is to be viewed under the microscope must, of course, be supported in some way—this is now usually done by placing it upon a glass slide, which on account of the transparency has a great advantage over other substances. These “slides” are almost always made of one size, viz., three inches long by one broad, generally having the edges ground so as to remove all danger of scratching or cutting any object with which they may come in contact. The glass must be very good, else the surface will always2 present the appearance of uncleanliness and dust. ”

“ Many objects for the microscope may be seriously injured by allowing the fingers to touch them—many more are so minute that they cannot be removed in this way at all, and often it is necessary to take from a mass of small grains, as in sand, some particular particle. ”

“ The method which is the most frequently made use of is the following:—Place the “gathering” containing the Diatomaceæ in a small glass or porcelain vessel, add strong nitric acid, and, by the aid of Bunsen’s burner or spirit-lamp, boil for some minutes. From time to time a drop of the mixture may be put upon a slide, and examined under the microscope to see if all foreign matter be got rid of. When the valves are clean, the vessel containing them must be filled with water, and the whole left for an hour or two, so that all the diatoms may settle perfectly. ”

“ Plants afford an almost inexhaustible treasury for the microscope, and many of them show their beauties best when mounted dry. When any of these also are to be mounted, care must be taken that they are thoroughly dry, otherwise the damp will certainly arise in the cell, and injure the object ”

“ Even with every care it is not possible to get rid of this annoyance occasionally.
For the purpose of mounting opaque objects “dry,” discs were at one time very commonly made use of. These are circular pieces of cork, leather, or other soft substance, from one-quarter to half inch in diameter, blackened with varnish or covered with black paper, on which the object is fixed by gum or some other adhesive substance. They are usually pierced longitudinally by a strong pin, which serves for the forceps to lay hold of when being placed under the microscope for examination. ”

“ Forceps are required in almost all microscopic manipulations, and consequently are scarcely ever omitted from the microscopic box, even the most meagrely furnished; but of these there are various modifications, which for certain purposes are more convenient than the usual form. The ordinary metal ones are employed for taking up small objects, thin glass, &c. ”

“ It is evident that any object placed betwixt them will be subject to continual pressure. The power of this may be regulated by the thickness and length of the whalebone. This simple contrivance is very useful.
Common watch-glasses should always be kept at hand. They are certainly the cheapest, and their transparency makes them very convenient reservoirs in which objects may be steeped in any liquid; as it saves much trouble to examine cursorily under the microscope, when the air-bubbles are expelled from insects, &c., &c. ”

“ When these are at any stage in which it is wished to preserve them, a few seconds’ exposure to the fire, as warm as the hand can comfortably bear, will stop the expansion, when the portion which we wish to mount should be cut off from the mass of salt by simply scratching the film around, and pure Canada balsam with the thin glass used. Breathing upon the film, or allowing the slide to become cold and attract the moisture from the atmosphere, will cause the crystallization to extend, and sometimes greatly rob the effect ”

“ When mounting an object in any of these cells, the glass must be thoroughly cleaned, which may be done with a cambric handkerchief, after the washing mentioned in Chapter I. If the object be large, the point of a fine camel-hair pencil should be dipped into the gum solution, and a minute quantity of the liquid deposited in the cell where the object is to be placed, but not to cover a greater surface than the object will totally hide from sight. ”