m I Vf Trrr ^\ HALF-HOUES WITH THE MICEOSCOPE. "mm Tuffen^st s"! adnat. VfV/est mm Landcn Eobert JIaxdwicikfi,1860. L- Ji HALF-HOURS '^ WITH THE MICROSCOPE; BEING A POPULAR GUIDE TO THE USE OF THE MICROSCOPE AS A MEANS OF AMUSEMENT AND INSTRUCTION. BY EDWIN LANKESTER, M.D. ILLUSTRATED FROM NATURE_, BX TUFFEN WEST. -^ nSTE-W EX)ITI0 2T. LONDON : EOBEET HAEDWICKE, 192, PICCADILLY ^ AND ALL BOOKSELLERS. ^/ LONDOIT : WYMAN AND SONS, PEINTEES, GREAT QUEEM STEEEXj LINCOLN'S-INJf FIELDS, W. C. PREFACE TO THIED EDITION. -•o*- The success of this little work has greatly exceeded the author's most sanguine expectation, upwards of 7,000 copies having been already sold. A new edition being now required, he gladly avails himself of this opportunity to make several important additions, consisting of fresh matter interspersed with woodcuts, descriptive of the construction of the Compound Microscope and its various appendages. The Publisher hopes that it may, in its present shape, meet with the same favorable reception, and prove a still more useful and reliable guide to the Amateur Microscopist. 8, Savile Row. Xv^ '^^ >v E. L. uu: Ll^ ' '^' CONTENTS. CHAPTER L pagp A HALF-HOUR ON THE STRUCTURE OP THE MICROSCOPE. . 1 CHAPTER II. A HALF-HOUR WITH THE MICROSCOPE IN THE GARDEN.. 30 CHAPTER III. A HALF-HOUR WITH THE MICROSCOPE IN THE COUNTRY. . 47 CHAPTER IV. A HALF-HOUR WITH THE MICROSCOPE AT THE POND-SIDE 56 CHAPTER V. A HALF-HOUR WITH THE MICROSCOPE AT THE SEA- SIDE. . 67 CHAPTER VI. A HALT-HOUR WITH THE MICROSCOPE IN-DOORS 70 APPENDIX. THE PREPARATION AND MOUNTING OF OBJECTS S » 39743 DESCRIPTION OF PLATES. -•«»- In (he examination of these Plates the observer is requested to remember that they are not all drawn to the same scale. Some objects, adapted for low powers, are only magnified a few times, whilst smaller objects are magnified many hundred times. All objects, of course, vary in apparent size, according to the poicers with which they are examined. Descriptions of the objects will be found in the pages indicated. PLATE I. to face Title-page. FIG. PAGE 1. Vegetable cells with nucleus from apple 31 2. Cellular tissue from pith of elder 31 3. Stellate cell-tissue from rush 32 4. Flat tabular cell from surface of tongue 91 5. Ciliated cell from windpipe of calf 91 6. Human blood corpuscles 91 7. Blood corpuscles from fowl 92 8. Blood corpuscle from frog 92 9. Blood corpuscle from sole , 92 10. Blood corpuscle from beetle , 92 11. Filament of a species of Zygnema, a plant 60 a. Portion of a filament of the same, the cell- contents becoming changed into zoospores. 6o Zoospore more highly magnified. X THE MICROSCOPE. FIG. PAt^B 12. Filament of a species of Oscillatoria, a plant .... 60 a. Poi'tion more highly magnified. 13. Pandorina Morum, a plant 60 14. Volvox Globator, a plant 60 15. Euglena viridis, a plant, showing various forms which it assumes 61 16. AmceTja, an infusory sitoimalcule 69 a, h, c, show the various forms which this ani- malcule assumes ". 17. ActinopJirys Sol, the sun animalcule 62-69 18. Difflugia, an infusory animalcule 63 19. Arcella, an infusory animalcule 63 20. Lagena, a species of Foraminifer 69 21. Polystomella crispa, a species of Foraminifer 69 22. Globigerina, a species of Foraminifer 69 23. Ptosalina, from chalk, a Foraminifer 69 24. Living Rosalina, a Foraminifer g9 25. Texiilaria, a species of Foraminifer 69 PLATE II. to face page 32. 26. Uha in different stages of development gj a. Cells in single series. 6. Commencement of lateral extension. c. Portion expanded. 27. Cosmarium, a species of Desmid undergoing self- division. 28. Euastrum, a species of Desmid 57 29. Closterium, a species of Desmid *• 57 a. Undergoing self-division. 30. Desmidium, a species of Desmid 57 DESCKIPTION OF PLATF3. Xi FIG. PAGE 31. Pediastrum, a species of Desmid 57 32. Scenedesmus, a species of Desmid 57 33. Surirella nobilis, a species of Diatom 59 34. Pinnularia viridis, a species of Diatom 59 35. a. Navicula, a species of Diatom undergoing seK- division h. Front view of the same. 36. Melosira varians, a species of Diatom 59 37. 3felosira nummuloides undergo'mg seU-d'iv'ision .,., 59 38. Cosdnodiscus eccentricus, a species of Diatom 58 39. Paramecium Aurelia, an infusory animalcule 64 40. Vorticella nebidifera, an infusory animalcule 63 41. Rotifer vulgaris, a wheel animalcule 65 42. Stomates on a portion of cuticle of hyacinth leaf . . 32 43. Sinuous walled cells and stomates from under sur- face of leaf of water-cress 32 44. Cuticle of wheat straw with stomates 33 45. Cuticle from petal of geranium (Pelargonium). ... 33 46. Cuticle from leaf of a species of aloe 33 47. Spiral vessel from leaf-stalk of garden rhubarb .... 35 48. Ditto unrolled 35 49. Annular vessel from wheat root 35 50. Dichotomous spiral vessels 35 61. Dotted duct from common radish 35 52. Scalariform tissue from fern root ,, 35 53. Woody fibre from eidei' 35 Xli THE MICROSCOPE. PLATE III. to face page 40. PT3. P^GB! 5i. "Glandular" woody tissue 3i 55. Transverse section of glandular woody tissue .... 3i 56. Transverse section of oak 34 57. Long section of oak 34 58. Oblique section of oak 34 59. Section of cork - 35 60. Transverse section of coal 36 61. Lonsfitudinal section of coal 36 62. Wheat starch 37 63. Oat starch 37 64. Potato starch 37 65. Tous-les-mois starch 37 66. Indian corn starch 38 67. Sago starch 37 68. Tapioca starch 37 69. Acicular raphides from garden hyacinth 38 70. Bundle of ditto from leaf of aloe contained in a cell 38 71. Compound raphides from stalk of garden rhubarb. . 39 72. Tabular prismatic raphides from outer coat of onion 39 73. Circular crystalline mass from a cactus 39 74. Simple vegetable hair from leaf of a common grass 40 75. Rudimentary hair from flower of pansy 40 76. Simple club-shaped hair , 40 77. Club-shaped hair from leaf of dock 41 78. Hair from throat of pansy 40 79. a. Hair formed of two cells from flower of white dead-nettle 41 79, 6. Many-jointed tapering hair with nuclei from common groundsel 41 DESCRIPTION OF PLATES. xiil FIG. PAGE 80. Beaded hair of sow-thistle 41 81. Glandular hair from leaf of common tobacco 41 82. Hair from leaf of garden chrysanthemum 41 83. Kosette-shaped glandular hair from flower of verbena 41 84. Stellate hairs from the hollyhock {A Itlicea rosea).. 41 85. a. Stellate hair from leaf of lavender 41 85, 6. Hair from leaf of garden verbena, with warty surface 4 j 86. Hair from leaf of white poplar (Populus alba) . . , , 41 87. Base of a hair on a mass of cellular tissue 41 88, a. A sting from common nettle 42 88, 6. Portion of a leaf of Valisneria 42 PLATE lY. to face page 48. 89. Palmella cruenta — gory dew 48 90. Yeast plant 48 91. Portions of vinegar plant , 48 92. So-called cholera fungus obtained from the air. ... 48 93. Bed rust of wheat ... 49 94. Puccinia graminis — mildew 49 95. Penicillium glaucum — common mould 49 96. Botrytis from mouldy grape 49 97. Fungus from mouldy bread {Mucor Mucedo) .... 49 98. Fungus from human ear 49 99. Fungus from leaf of bramble {Phragmidium hul- hosum) 49 100. Vine blight {Oldium Tuckcri) 50 101. Potato blight {Botrytis infestans) 50 102. a. Pea blight {Erysiphe Pisi) 50 h. Asci and sporidia of pea blight 50 103. Fungus from a decayed Spanish nut 50 xiv THE MICROSCOPE. ria. PAGB 104. Curious fungus from oil casks 50 105. Ynn 230. Hair-like scale from clothes-motb, with three prongs St 231. Cartilage from mouse's ear 91 232. Transverse section of human bone 9( 233. Striped muscular fibre from meat 92 234. a. Liber fibre of flax, natural state 79 6. Ditto, broken across at short intervals. 235. Wool from flannel 7S 236. Silk 79 237. Cotton hair 79 23S. Crystal of honey 39 239. Thick crystal of ordinary sugar — same angles .... 39 240. Crystals of sugar from adulterated honey 40 241. Cuticle from berry of holly 33 242. Transverse section of whalebone 90 243. Transverse section of plum stone 31 244. Transverse section of testa of seed of Guelder rose 31 245. Fruit of groundsel — opaque 42 246. One hair of pappus of dandelion 42 247. Cottony hair of burdock 42 248. Portion of pappus of goat's-beard 42 249. Wood of young shoots of vine, the cells containing starch 33 250. Spiral fibres from testa of wild sage seed. ,,,»,,, 35 HALF-HOURS WITH THE MICEOSCOPE CHAPTER I. A HALF-HOUR ON THE STEUCTURE OF THE MICROSCOPE. The Microscope is often regarded merely as a toy, capable of affordiog only a certain amount of amusement. However much this might have been the case when its manufacture was less perfectly understood, it is now an instrument of so much importance that scarcely any other can vie with it in the interest we attach to the discoveries made by its aid. By its means man increases the power of his vision, so that he thus gains a greater know- ledge of the nature of all objects by which he is surrounded. What eyes would be to the man who is born blind, the Microscope is to the man who sees only with his naked eye. It opens a new world to him, and thousands of objects whose form and shape, and even existence, he could only ima- gine, can now be observed with accuracy. Nor is this increase of knowledge without great advantages. Take for instance the study of plants and animals. Both are endowed with what we call life : they grow and perform certain living functions ; but as to the mode of their growth, and the way in which their functions were performed, little or nothing was known till the Microscope revealed their mmute structure, and showed how their various narts were related to each other Tha 2 THE STRUCTURE OP Microscope lias thus become a necessary instrument in the hands of the botanist, the physiologist, the zoologist, the anatomist, and the geologist. Let us. then, endeavour to understand how it is this little instrument has been of such great service in helping on the advancement of science. Its use depends entirely on its assisting the human eye to see — to see more with its aid than it could possibly do without it. This it does by enabling the eye to be brought more closely in contact with an object than it otherwise could be. Just in proportion as we bring our eyes close to objects, do we see more of them. Thus, if we look at a printed bill from the opposite side of a street, we can see the larger letters only ; but if we go nearer we see the smaller letters, till at last we get to a point when we can see no more by getting closer. Now suppose there were letters printed on the bill so small that we could not see them with the naked eye, yet, by the aid of a lens — a piece of convex glass — we could bring our eyes nearer to the letters, and see them distinctly. It would depend entirely on the form of the lens, as to how close we could bring our eyes to the print, and see; but this great fact will be observed, that the nearer we can get our eyes to the print, the more we shall see. The most important part of a Microscope, then, consists of a lens, by means of which ihe eye can be brought nearer to any object, and is thus enabled to see more of it. Magnifying-glasses and Simple Microscopes consist mainly of this one element. In order, however, to enable the eye to get as close as possible to an object, it becomes convenient to use more than one lens in a glass through which we look. These lenses, for the sake of convenience, are fixed in a brass frame, and attached to the Simple Microscope ; when there are two lenses they THE MICROSCOPE. 3 are called doublets, and when three they are termed triplets. The magnify ing-glasses which are made to be held in the hand, frequently have two or three lenses, by which their power may be increased or decreased. Such instruments as these were the first which were employed by microscopic observers; and it is a proof of the essential nature of this part of the Microscope, that many of the greatest discoveries have been made with the Simple Mi- ^croscope. The nearer the glass or lens is brought to an object, so as to enable the eye to see, the more of its details will be observed. So that when we use a glass which enables us to see within one inch of an object, we see much more than if we could bring it within only an inch and a half or two inches. So on, till we come to distances so small as the eighth, sixteenth, or even twentieth of an inch. Although a great deal may be seen by a common hand-glass, such as may be purchased at an optician's for a few shillings, yet the hand is unsteady ; and if these glasses were made with a very short focus, it would be almost impossible to use them. Besides, it is very desirable, in examining objects, to have both hands free. On these accounts the glasses, which in such an arrangement are called object- glasses (see fig. 3), are attached to a stand, and placed in an arm, which moves up and down with rack- work. In this way, the distance of the object from the glass can be regulated with great nicety. Under- neath the glass, and attached to the same stand, is a little plate or framework, to hold objects, which are placed on a slide of glass. This is called the stage. (Fig. 1, 6^.) Sometimes rack-work is added to this stage, by which the objects can be moved upon it backwards and forwards, without being moved by the hand. Such an arrangement as this i» B 2 4 THE STRUCTURE OF called a Simple Microscope. Of course many other things may be added to it, to make it more conveni- ent for observation ; but these are its essential parts. But, although the Simple Microscope embraces the essential conditions of all Microscopes, and has, in the hands of competent observers, done so much for science, it is, nevertheless, going out of fashion, and giving way to the Compound Microscope. (Fig. 1, p. 5.) This instrument, as might be inferred from its name, is much more complicated than the Simple. Microscope, but it is now constructed with so much accuracy, that it can be used with as great cer- tainty and ease as the Simple Microscope itself. In order to understand the mechanism of the Compound Microscope we must first of all study the principles on which it is constructed. If we take a common convex lens and place any small object on one side of it, so as to be in its focus, and then place on the other side a sheet of white paper, we shall find at a certain point that an enlarged picture of the object will be produced on the paper ; and this is the way in which pictures are formed by the camera of which the photographic artist avails himself for his portraits and sun-pictures. Now i^ we look at this picture with another lens of the same character but of somewhat less magnifying power, we shall obtain a second picture larger than the first, and this is the principle involved in the Compound Microscope. The superiority of this instrument over the Simple Microscope consists in an increase of magnifying power. There is, how- ever, a limit to the utility of this magnifying power; for when objects are greatly magnified they become indistinct. This is seen in the Oxyhydrogen and Solar Microscopes, where the images are thrown, by means of highly magnifying lenses, on a white sheet; and, although made enormously large, their details THE MICROSCOPE. are mucli less clear than when looked at by a lens magnifying much less. Another advantage of the Fig. \* Compound Microscope. Compound Microscope is the distance at which thft eye is placed from the object, and the facility with * In this little work we have purposely abstained fron. mentioning either the names or the Microscopes of our principal makers, lest we should thereby seem to give a 6 THE STRUCTURE OP wLich the hands may be used for all purposes of manipulation. A brief description, aided by the accompanying illustration, will, it is hoped, suflSce to make the beginner acquainted with the various parts of this important instrument. We have already mentioned that when powerful lenses are used in the examination of small objects the hand is not sufficiently steady to give a firm support to the lens employed, and this is equally true of the hand that holds the object. It is also essentially requisite to have both hands free, for the purpose of manipulation. Hence it becomes necessary to devise some mechanical means for the support of both the lens and the object. How these wants have been supplied by the enterprising skill and ingenuity of our opticians will be best seen as we describe the various parts of which the Compound Microscope consists. The most important part of the instrument is undoubtedly that which carries the various lenses or magnifying powers. These are contained in the interior of the tube or body, A, which is usually constructed of brass, and from 8 to 10 inches in length. At the upper end of the tube is the eye- piece, B, so named from its proximity to the eye of the observer. It consists of two plano-convex lenses, set in a short piece of tubing, with their flat surfaces turned towards the eye, and at a distance from each other of half their united focal lengths. The first of these lenses is the eye-glass, while that nearest the objective is termed the field lens. The use of the latter is to alter the course preference to any. The general excellence of these instru- ments is so well known and the names of their makers are so universal that the student will find no difficulty in provid- ing himself with an efficient instrument at a moderate cost. THE MICROSCOPE. of the light's rays in their passage to the eye, in such manner as to bring the image formed by the object-glass into a condition to be seen by the eye- ^i^lass. A stop also is placed between the two lenses in such a position that all the outer rays, which pro- duce the greatest amount of distortion, arising from spherical and chromatic aberration, are cut off. The short tube carrying the lenses (fig. 2) slides freely, but without looseness, into the upper end of the com- pound body, J., an arrangement which affords a ready and convenient method for changing the eye-piece. Compound Microscopes are generally fitted up with two eye-pieces, the one deep and the other shallow. The last has its lenses close together, and magnifies the most, whilst the other has them far- ther apart, and magnifies less. In the use of these eye-pieces, it should never be forgotten that the one which magnifies least is generally the most trust- worthy. At the opposite end of the tube A is the object- glass G. The use of this lens is to collect and bring to a point the rays of light that proceed from any object placed in its focus. At this point an enlarged image of the object will be formed in the focus of the eye-glass. We have only to look through the latter at the picture thus formed in order to obtain a second image larger than the first. And this is the way in which minute objects are made to appear so much larger than when seen by the unassisted eye. It will at once be seen how Fig. 2. Eye-piece. 8 THE STRUCTURE OF much of the utility of a Microscope depends on good object-glasses. Where they are faulty, the image they form is also faulty ; and when these faults in the first image are multiplied by the power of the eye-piece, they become — like the faults of our friends when viewed through a similar medium — of grreat magnitude. A good object-glass may be known by its giving a clear and well-defined view of any object we may wish to examine ; while a bad lens may be equally well known by the absence of these qualities. In short, a badly constructed objective is more apt to mislead than to guide the student, by the fictitious appearances it creates — appearances that may be erroneously taken for realities, which have no exist- ence in the object itself. The object-glasses of our best opticians consist of several lenses arranged in pairs, set in a small brass tube. A screw at one end serves to attach them to the lower extremity of the compound body, A. (Fig. 3.) The body of the Microscope is supported by a stout metal arm, D, into the free end of which it screws. The opposite end of the arm is secured to the stem, B, by a screw, on which it moves Fig. 3. Object^lass. ^« ^^ ^ P^^^^' ^J ^^^^ "^^^^^ the tube of the Microscope can be turned away from the stage — an arrangement that gives this form of Microscope an advantage over those that are not so constructed. To the stem, U, which works up and down a hollow pillar by rack-work and pinion, is attached the stage, G. This, in its simplest form, consists of a thin flat plate of brass, for holding objects undergoing ex- THE MICROSCOPE. amination. In the centre is a circular opening, for the passage of the light reflected upward by tho mirror, H, There is also a sliding ledge, // against this the glass slide, on which the object is mounted, rests, when the Microscope is inclined from the perpendicular. In a stage of this kind the various parts of an object can only be brought under the eye by shifting: the slide with the fingers. But in more expensive instruments the stage is usually con- structed of one or two sliding plates, to which motion is given by rackwork and pinion ; the whole being brought under the hand of the operator by two milled heads, a mechanical arrangement which enables him to move with ease and certainty the object he may wish to investigate. Underneath the stage is the diaphragm, K, a contrivance for limiting the amount of light supplied by the mirror, H. lb consists of a thin, circular, flat plate of metal, turning on a pivot, and perforated with three or four cir- cular holes of varying diameter (^fig. 4), the largest only being equal to the aperture in the stage. By turning the plate round, a succession of smaller openings is brought into the centre of the stage, and in one position of the diaphragm the light is totally excluded. By this small but useful contrivance the IMicroscopist can adjust the illumination of the mirror to suit the character of the object he may be investiga- ting. In some Microscopes the diaphragm is a tix- Fiy. 4. Diaphragm. 10 THE STRUCTURE OF Fig. 5. Diaphragnr., tiire, but in the better class of instruments it is simply attached to the under part of the stage by a bayo- net catch, or by a sliding plate of me- tal (fig. 5), and can be readily removed therefrom when it is desirable to employ other methods of illumi- nation. In working with the Microscope it is necessary to adopt some artificial means for ensuring a larger supply of light than can be obtained from the natural diff'ased light of day, or from a lamp or candle. For this purpose the Microscope is fur- nished with a double mirror, H, having two reflect- ing surfaces, the one plane and the other convex. The latter is the one usually employed in the illu- mination of transparent objects ; the rays of light which are reflected from its concave surface are made to converge, and thus pass through the object in a condensed form to the eye. The plane mirror is used generally in conjunction with an achromatic condenser, when parallel rays only are required. The whole apparatus is attached to that portion of the hollow pillar continued beneath the stage, in such a manner that it can be moved freely up and down the stem that supports it. This motion enables the Microscopist to regulate the intensity of his light by increasing or decreasing the distance between the mirror and the stage ; while the peculiar way in which the mirror itself is suspended on two points of a crescent-shaped arm, turning on a pivot, gives an almost universal motion to the reflecting surfaces. The observer by this means can secure any degree of oblique illumination he THE MICROSCOPE. 11 may require for the elucidation of the structure undergoing examination. We next come to the stand, which, though the most mechanical, is at the same time a very impor- tant part of the Compound Microscope. On the solidity and steadiness of this portion of the instru- ment depends in a great measure its utility. The form generally adhered to is that represented in our diagram (fig. 1, p. 5.) It consists of a tripod base, -P, from which rise two flat upright pillars, 0. Between these* on the two hinge-joints shown at L, is sus- pended the whole of the apparatus already described : namely, the body carrying the lenses, the arm to which it is attached, the stage, and the mirror underneath it. By this contrivance the Microscope can be inclined at any angle between a vertical and horizontal position — an advantage which can be duly appreciated by those who work with the instrument for two or three hours at a time. Close to the points of suspension are the milled heads, M ; these are connected with a pinion working in a rack cut in the stem, E. By turning the milled heads thf> tube is made to approach or recede from the stage until the proper focus of the object-glass is found. This is termed the coarse adjustment, and is gene- rally used for low powers, where delicate focussing is not required. But when high magnifying powers are used, that require a far greater degree of pre- cision, we have recourse to the fine adjustment, iV, which consists of a screw acting on the end of a lever. The head of the screw by which motion ic communicated to the object-glass is divided into ten equal parts, and when caused to rotate through any of its divisions slightly raises or depresses the tube, carrying the objective with it. As the screw itself contains just 150 threads to an inch one revolution of its head will cause an alteration of the 150th 12 THE STRUCTURE OF of an inch in the distance of the lens from the object. When moved through only one of its divisions we obtain a result equal to the 1500th of an inch, and by causing it to rotate through half a division we secure a movement not exceeding the 3000th part of an inch in extent. Such nicety in the adjustment of the optical part of the Micro- scope may seem to the beginner unnecessary, but when he comes to work with high powers he will find that he needs the most delicate mechanical contrivances to enable him to secure the proper focus of a sensitive object-glass. But this is not the only use to which we can put the fine adjustment. The same process that serves to re- gulate the focusof a lens will also enable us to measure pretty accurately the thickness of an object or any of the small prominences or depressions found in its structure. By observing the number of divisions through which the head of the screw is made to pass while changing the focus of the object-glass from the bottom to the top of any small cavity or prominence we get a tolerable notion of its depth or height, &c. Connected with this apparatus is a special contrivance for protecting the object-glass to some extent from injury. It will sometimes happen, even with the most careful, when using high powers, that the lens is brought down with some force in contact with the glass cover that protects the object. This risk is not unfrequently incurred by admitting to one's study incautious friends, whose confidence is only equalled by their ignorance; who although they may have never seen a Microscope before, will proceed to turn it up and down with a force sufficient to crack the lens. Such friends would have sufficient confidence in themselves to take the command of a man-of-war, even though it were the first time in their lives THE MICROSCOPE. 13 tliey had been on board a ship. Strict injunctions must be laid on all such not to approach the table until the instrument is quite ready for them to take a peep, coupled with a polite request that while doing so they will keep their hands behind them. A provision has been made which to some extent provides for such an emergency. The object-glass itself is screwed into a short tube, that fits accu- rately the lower end of the compound body and slides freely within it, being kept down in its place by a spiral spring, which presses upon it from behind. On the application of a slight force or resistance to the object-glass the spring tube immediately yields, within certain limits, to the pressure, carrying with it the lens, which is thus often saved from destruction. Object-glasses of various degrees of magnifying power and excellence of workmanship are supplied with the Microscope, and may be purchased separately, according to the wants and resources of the student. It will be found that for all ordinary purposes the 1-inch and ■f-inch objectives are the most useful powers. A substitute for the intermediate powers may be obtained by pulling out the draw-tube and using the higher eye-pieces. This method, though not so satisfactory in its results as the use of separate object-glasses, may be resorted to where a series of objectives are not within the reach of the observer. THE BINOCULAR MICROSCOPE. Since the invention of the Stereoscope attempts have been made to apply the Binocular principle in the construction of the Compound Micro- scope. After some failures this desideratum has been successfully achieved by Mr. F, H. Wenham, a gentleman well known to microscopists by 14 THE STRUCTURE OF the fertility of his resources and the ingenuity of his inventions in connection with the Microscope. It is to him that we are indebted for a Microscope that enables us to see objects in a natural manner, namely, with both eyes at once. Hitherto the ordinary single-tubed Microscope reduced the ob- server to the condition of a Cyclops. Although gifted with a pair of eyes he found it impossible to avail himself of this plurality of organs. He was condemned by the very nature of his Microscope to peer perpetually with a single eye through its solitary tube ; but thanks to Mr. Wenham all this is changed. We have now the satisfaction of using a double-tubed Microscope that not only gives em- ployment to both eyes at once, but presents us with effects unknown and unattainable by the ordinary instrument. We no longer gaze at a flat surface, but a stereoscopic image stands out before us with a boldness and solidity perfectly marvellous to those who have only been accu-stomed to the ordinary single-tubed Microscope. " No one," says a writer in ' The Popular Science Review,' " can fail to be struck with the beautiful appearance of objects viewed under the Binocular Microscope. Its chief application is to such objects as require low powers, and can be seen by reflected light, when the wonderful relief and solidity of the bodies under observation astonish and delight even the adept. Foraminifera, always beautiful, have their beauties increased tenfold ; vegetable struc- tures, pollen, and a thousand other things, are seen in their true lights, and even diatoms, we may pre- dict, will receive elucidation, as to the vexed ques- tions of the convexity or concavity of their infinitely minute markings. The importance of the Binocular principle is especially apparent when applied to anatomical investigation. Prepared Microscopic THE MICROSCOPE. 15 injections exhibit under the ordinary Microscope a mass of interlacing vessels, whose relation, being all on the same plane, it is not easy to make out with any degree of satisfaction. But placed under the Binocular they at once assume their relative position. Instead of a flat band of vessels, we now see lnyer above layer of tissue ; deeper vessels an- astomosing with those more superficial ; the larger vessels sending branches, some forward and some backward, and the whole injection assumes its natural appearance, instead of being only like a picture.^^ Fortunately for the possessors of the ordinary Microsco})e the Binocular ar- rangement can be readily ad- apted to this instrument at a cost of a few pounds. The extra tube and eye-piece are attached to the ordinary com- pound body by a bayonet catch, and can be removed therefrom when not required; at the same time the hole in the main body being closed by a shutter, the instruDient is reduced to its original condition. The same effect, however, is produced without the removal of the additional tube, by simply withdrawing the prism that bisects the light, which being no longer divided passes up the original tube as before. The accompanying diagram (fig. 6) — a section of the Bin- ocular— will give the reader a Fig. 6. Section of correct notion of the mecha- Binocular Microscopa 16 THE STRUCTURE OJ nism of tlie instrument. Let G represent the body of the ordinary Microscope and B the secondary tube attached to the side of the former, which it will be seen has a portion of its surface cut away at the point of junction, F, as a means of commu- nication between them. The eye-pieces and draw- tubes are seen at D and E. The object-glass G is attached to the ordinary tube C in the usual way. Just above it is the small prism, J., mounted in a brass box, and so constructed as 10 slide into an opening in the tube at the back of the object-glass. By this arrangement it will be found that while one half of the light passes up the tube unobstructed the other half must first pass through the prism, where, after undergoing two re- flections (fig. 7), it es- capes in the direction of the additional tube B. The dotted lines in the diagram show the direction the light takes in its passage to the eyes. At H the rays are seen to cross each other. Those from the left side of theobject-glass traverse the ^ , , !f' .' ^ . right tube, while those from Double-reflecting Prism. ^^^ ^.^^^^ ^.^^ ^^ ^^^ ^^^^ are projected up the left tube. In using the Binocular it must be remembered that the eyes of different individuals vary in their distance from each other. It will thus be seen that some contrivance is necessary to enable us to ft/ increase or decrease the distance between the eye- pieces to suit the requirements of all. This is accomplished by the two draw-tubes, I) and JS^ ivhich carry the eye-pieces. When drawn out, the THE MICROSCOPE. 17 latter are made to diverge, and when pushed in they converge. In this way any intermediate distance can be obtained to suit every kind of vision. Where a Binocular Microscope is in daily use it will sometimes be necessary to withdraw the prism from the tube, to cleanse it from dust and other impurities gradually contracted by use. Whenever this may be necessary great care should be taken to employ no substance likely to scratch its highly polished surfaces; for on these being preserved intact in a great measure dej^nds the efficiency of the in- strument. We know of nothing better adapted for removing impurities than a clean silk or cambric handkerchief, which, when not in use, should be kept in a closely-fitting drawer, to protect it from dust. There seems to be little doubt that this lately improved form of the Compound Microscope will eventually supersede all others. This opinion also seems to be entertained by the inventor himself, whose words we quote : — " The numerous Microscopes that have been altered into Binoculars, in accordance with my last principle, and also the large quantity still in the course of manufacture, will, I think, justify me in making the assertion, without presumption, that henceforth no first-class Microscope will be con- sidered complete unless adapted with the Binocular arrangement." The Compound Microscope is now, undoubtedly, one of the most perfect instruments invented and used by man. In the case of all other instruments, the materials with which they are made and the defects of construction are drawbacks on their per- fect working ; but in the Compound Microscope we have an instrument working up to the theory of its construction. It does actually all that could C 18 THE STRUCTURE OP be expected from it, upon a correct theory of the principles upon which it is constructed. Neverthe- less, this instrument did not come perfect from its inventor's hands. Its principles were understood by the earlier microscopic observers in the seventeenth and eighteenth centuries, but there were certain drawbacks to its use, which were not overcome till the commencement of the second quarter of the present century. These drawbacks depended on the nature of the lenses used in its construction. The technical term for the defects alluded to are chromatic and spheri- cal aberration. Most persons are acquainted with the fact that, when light passes through irregular pieces of cut glass — as the drops of a chandelier, — a variety of colours is produced. These colours, whfln formed by a prism, produce a coloured image called the spectrum. Now, all pieces of glass with iiTegular surfaces produce, more or less, the colours of the spectrum when light passes through them ; and this is the case with the lenses which are used as object-glasses for Microscopes. In glasses of defective construction, every object looked at through them is coloured by the agency of this property. The greater the number of lenses used in a Microscope, the greater, of course, is the liability to this colouring. This is chromatic aberration ; and the liability to it in the earlier- made Compound Microscopes was so great that it destroyed the value of the instrument for purposes of observation. Again, the rays of light, when passing through convex lenses, do not fall — when they form a picture — all on the same plane; and therefore, instead of forming the object as presented, pro- duce a picture of it that is bent and more or less distorted. This is spherical aberration, and a fault THE MICROSCOPK 19 which was liable to be increased by the number of glasses, in the same way as chromatic aberration. This defect also is increased in Compound Micro- scopes ; and formerly, the two things operated so greatly to the prejudice of this instrument that it was seldom or never used. Gradually, however, means of improvement were discovered. These defects were rectified in tele- scopes; and at last a solution of all the diflaculties that beset the path of the Microscope-maker was afforded by the discoveries of Mr. Joseph Jackson Lister, a gentleman engaged in business in London, who, in a paper published in the PhilosojMcal Transactions for 1829, pointed out the way in which the Compound Microscope could be con- structed free from chromatic and spherical aberra- tion. This is done by such an arrangement of the lenses in the object-glass, that one lens corrects the defects of the other. Thus, in object-glasses of the highest power, as many as eight distinct lenses are combined. We have, first, a triplet, composed of two plano-convex lenses of crown-glass, with a plano-concave of flint-glass between them. Above this is placed a doublet, consisting of a double convex lens of crown, and a double concave one of flint-glass. At the back of this is a triplet, which consists of two double convex lenses of crown- glass, and a double concave one of flint placed be- tween them. Such are the combinations necessary to correct the defects of lenses when employed in Compound Microscopes. It is this instrument, then, which is most com- monly employed at the present day, and to which we are indebted for most of the recent progress in microscopic observation. In using the Microscope, a great variety of acces- sory apparatus may be employed to facilitate the 20 THE STRUCTURE OF various objects which the observer has in view. As this is a book for beginners, we shall only- mention a few of these. Microscopes are generally supplied with small slips of glass, three inches long and one inch wide. These are intended to place the objects on which are to be examined. They are either used tempo- rarily or permanently with this object in view, Fig. 8. Forceps. and are called slides. "When used temporarily, an object, such as a small insect, or part of an insect, Fig. 9. Bull's-eye Condenser. is placed upon the middle of it ; and it may be either placed immediately upon the stage at the THE MICROSCOPE. 21 proper distance from the object-glass, or a drop of water may be placed on the slide, and a piece of thinner glass placed over the object. This is the most convenient arrangement, as yoii may then tilt your Microscope without the slide or object falling off. Objects, when placed under the Microscope, are of two kinds — either transparent or opaque. When they are opaque, they may either be placed upon the slips of glass, or put between a small pair of forceps (fig. 8), which are fijced to the stage of the Microscope, and the light of a window or lamp allowed to fall upon them. This is not, however, sufficient, generally, to examine things with great accuracy ; and an instrument called a condenser (tig. 9) is provided for this purpose. It consists merely of a large lens, which is sometimes fixed to the stage, or has a separate stand. Its object is to allow a concentrated ray of light to be thrown on the opaque object whilst under the object-glass of the Microscope. This is called viewing objects by rejected light. Transparent objects, ©n the other hand, are viewed by transmitted lights reflected from the plane or concave surface of the mirror beneath the stage. The object of this mirror, which is called the reflector, is to cat^*.h the rays of light and con- centrate them on the object under the Microscope. The rays of light thus pass through the object, and its parts are seen much more clearly. Another convenient piece of apparatus is an animalcule cage. This consists of a little brass box, inverted, to the bottom of which is attached a piece of glass. Over this, again, is placed a lid or cover, with a glass top. The cover can be made to press on the glass beneath, and an object being placed between the two glasses, can be submitted 22 THE STRUCTURE Or to any amount of pressure thought necessary, (i^ig. 10.) This IS a very important instrument for examining minute Crustacea, animalcules, zoophytes, and other living and moving objects, especially when they live in water. Fig. 10. Animalcule Cage or Live Box. In the use of the cage and the slide, care must be taken not to break them by turning the object- glass down upon them. It is sometimes a difficult thing, when the object-glass has a focus of not more than a quarter or eighth of an inch, to adjust It to exactly the point at which the object is best seen, by means of the coarse handles on the rack- work. For this reason the Microscope has been provided with a fine adjustment, by which the object-glass is moved down on the object in a much slower and more gradual manner, and the destruction of an expensive objective glass is often thus prevented. The picture of the object brought to the eye in the Compound Microscope is always the wrong end upwards. _ That is, the picture is always the re'verse in the Microscope to what it is with the naked eye. You need constantly to be aware of this, especially if you are going to dissect an object under the Microscope, as your right hand becomes left, and your left right. The observer, however, soon gets accustomed to this, and it creates no difficulty ulti- mately. But science constantly attends on the THF MICROSCOPE. 23 Microscope, and ministers to its slightest defects. A little instrument called an erector, composed of a lens which reverses the picture once more, is supplied by the optician, and can be had by those who practise the refinements of microscopic observation. Another instrument which will be found of con- siderable service even to the beginner with the Microscope, is a micrometer. This is an instrument for measuring the size of objects observed. Exag- gerated notions about the smallness of objects are very prevalent ; and as it is almost impossible to say accurately how small an object is without some means of measuring, a Micrometer becomes essen- tial where accuracy is desired. This i« effecte'' by having some object of known size to compare with the object observed. The most convenient instru- ment of this kind is a glass slide, on which lines are drawn the hundredth and thousandth of an inch apart. If this slide, which is called a stage micrometer, is laid over an object, or the object placed upon it, its relation to the ruled lines will be easily seen, and the size computed accordingly. Many other forms of micrometer have been in- vented, but this is one of the simplest and most easily used. It is a good plan to make drawings of all objects examined, or at any rate those which are new to the observer. A note-book should be kept for this purpose, and what cannot at once be identified by the object, may afterwards be so by the drawing. All persons, however, have not the gift of drawing, and for those who need assistance in this way, the camera lucida has been invented. This instrument is applied to the tube of the Microscope when placed at right angles with the stem, in such a way that a person looking into it sees the object directly 24 THE STRUCTURE OP under his eye, so that he may easily draw its form on a piece of paper placed underneath. (Fig. 11). Amongst the ac- cessory apparatus are various arrangements for concentratinof the ' — light on the objects which are placed for examination under the Microscope. One of these combinations is called the achro- matic condenser. This consists of a series of lenses, which are placed between the mirror and the stage, and which may con- sist of an ordinary object-glass. The stages of the larger Fig. n. Camera Lucida, kinds of Microscopes are fitted up with a screw or slide, by which the condenser can be fastened beneath and adjusted to the proper focus for throwing light on the otDJect examined. Instruments have also been in- vented, called illuminators, which are intended to supplement or assist the mirror in throwing light on the object. These are things, hov/ever, about which the begfinner need not trouble himself. Tbey are amongst the apparatus which contribute to the perfection of the Microscope, but are not amongst its necessary accompaniments. The same may be said of the ^x)/a?'^5;2?^^ ap~ paratus. The use of polarized light adds greatly to the beautiful appearance of many objects under the Microscope, but it is only in a very few i THE MIOROSCOPl 25 as to instances in -whicli it can be said to furnisli a means of distinguishing one object from the other. It may, therefore, be left to the time when the observer has gone through some little practice with his instrument, and is inclined to buy the necessary apparatus. Having said thus much with regard to apparatus, we will now give some direc- tions for the use of the Mi- croscope under ordinary cir- cumstances. The Microscope may be either used by the light of the sun in the day- time, or at night by some form of artificial light. It is best used by daylight, artificial light is likely tire the eyes. Having determined to work by daylight, some spot should be selected near a window, out of the direct light of the sun, in which to place a small, firm, steady table. On this the Micro- scope should be placed, and the object-glass should be screwed on to the tube. The mirror should be then ad- justed so as to throw a bright ray of light on to the object-glass. The eye-piece having been previously placed 2. Dipping Tube«. at the top of the tube, the Microscope is now ready to receive a transparent object. If the object to be examined is an animal- 26 THE STRUCTURE OP cule, it may be conveyed to the animalcule-cage by means of a glass tube, called a pipette or dipping-tube (fig. 12), which should be dipped into the water where the object is contained, with the fin- ger covered over the upper orifice, so that no air can escape. By taking the finger off when the tube is in the water, the fluid will rush into the tube, and with it the object to be examined. The finger is again applied to the top of the tube, and the fluid ob- tained conveyed to the animalcule cage. Only such a quantity of the water should be allowed to fall out of the tube on to the cage as will enable the observer to put on the cover of the cage without pressing the fluid out at the sides of the cage. If the water is thus allowed to overflow, it runs over the glasses of the cage, and thus obscures vision. An object or objects having been thus placed in the cage, it is conveyed to the stage, and placed in such a position that the ray of light passing from the mirror to the object-glass may pass through it. This having been done, the observer must now place his eye over the eye-piece, and use the screw in the tube, and move the object-glass downwards until he gets a clear view of objects moving in the water. This is called focussing. The glass may then be moved up or down, in order that the best view of the object may be obtained. "When the object-glass is one of high power, the fine adjust* Tnent may be used for this purpose. When the proper focus is obtained, the object may be moved up or down, right or left, with the hand, or by the aid of the screws which are employed in the various forms of what are called inoveahle stages. When objects not requiring the live-box or ani- malcule cage are to be observed, they may be transferred to the glass slide by aid of a thin slip of wood, or a porcupine-quill moistened at the end, THE MICROSCOPE. 27 or by a pair of small forceps. (Fig. 8.) Some trans- parent objects may be seen without any medium, but generally it is best to place them on the slide with a drop or two of clean water, which may be placed on it with a dipping-tube. When water is used, it will generally be found best to cover the object with a small piece of thin glass. Small square pieces of thin glass are sold at all the opticians' shops for this purpose. The object is then placed under the object-glass as before. In order to render objects transparent, so that they may be viewed by transmitted light, very thin sections of them should be made. This may be effected by means of a very sharp scalpel, or a razor. "When objects are too small to be held in the hand to be cut, they may be placed between two pieces of cork, and a section of them made at the same time that the cork is cut through. Sometimes it is found desir- able to unravel an object under the Microscope. If this is the case only a low power should be used, and the object may be slide, with- placed on a glass out any glass over, and two needles with small wooden han- dles employed — ordinary sew- ing needles, with their eyes stuck in the handle of a hair pencil, will answer very well. (Fig. 14.) Even when dissection is not to be carried on under the Microscope, a pair of needles of this Fig. 14. Dissecting Needles. 28 THE STRUCTURE OF sort, for tearing minute structures in pieces, will be found very useful. When opaque objects are to be examined, the light from the mirror may be shut off, and the aid of the bull's-eye condenser called in. The object being secured in the forceps attached to the stage (fig. 15), or laid upon a slide, the| light is allowed to fall on it through the condenser. (Fig. 9.) The object-glass must be focussed in the same manner as for transparent objects, till the best distance is secured for examining it. The petals of plants, the wings and other parts of insects, with many other objects, can only be examined in this way. Fig. 15. Stage Forceps. Even the beginner will find it useful to keep by him some little bottles, containing certain chemical re-agents. Thus, a solution of iodine is useful to apply to the tissues of plants, for the purpose ot ascertaining the presence of starch. This solution may be made by adding five grains of iodine and five grains of iodide of potassium to an ounce ot distilled water. Strong sulphuric acid will be found useful in rendering soff the tissues of both plants and animals ; and in conjunction with iodine it is a test for the presence of cellulose, the sub- stance that forms the walls of the cells of plants. In order to apply this test, the tissue should be first touched with the sulphuric acid, and on the applicatian afterwards of the solution of iodine lihe blue colour of starch becomes evident. The THE MICROSCOPE. 29 sulphuric acid has the power of converting the celhilose into starch. The strong solution of potash (liquor potassse) can also be employed with advantage in softening and making clear opaque animal and vegetable sub- stances. Nitric acid has even a greater solvent power than sulphuric acid, and may be used for the same purposes. While using these powerful acids great care should be taken to prevent the trans- parency of the object-glass becoming impaired by contact with the acids, or by long exposure to their vapours. ?>0 A HALF-nOUR WITH TIIB ' CHAPTER II. A HALF-HOUR WITH THE MICROSCOPE IN THE GARDEN. Amongst the objects which can be examined by the Microscope, none are more easily obtained than plants. All who have a Microscope may not be fortunate enough to have a garden ; but plants are easily obtained, and even the Londoner has access to an unbounded store in Covent Garden. We will, then, commence our microscopic studies with plants. On no department of nature has the Microscope thrown more light than on the struc- ture of plants; and we will endeavour to study these in such a manner as to show the importance of the discoveries that have been made by the aid of this instrument. If we take, now, a portion of a plant, the thin section of an apple, or a portion of the coloured parts of a flower, or a section of a leaf, and place It, with a little water, on a glass slide under the Microscope, we shall see that these parts are com- posed of little roundish hollow bodies, sometimes pressed closely together, and sometimes loose, assuming very various shapes. These hollow bodies are called "cells," and we shall find that all parts of plants are built up of cells. Sometimes, however, they have so far lost their cellular shape that we cannot recognize it at all. Nevertheless, all the parts we see are formed out of cells. Cells tolerably round, and not pressed on each other, may be seen in most pulpy fruits. In fact, with a little care in making a thin section, and placing MICROSCOPE m THE GARDEN. 31 it under the Microscope, the cellular structure of plants may be observed in all their soft parts. If, now, we take a thin section from an apple, or other soft fruit, or from a growing bud, or tuberous root, as the turnip, we shall find that many of the cells contain in their interior a "nucleus," or central spot, a representation of which is seen from the cells of an apple in figure 1 of the first plate. This nucleus is a point of great import- ance in the history of the cell, for it has been found that the cell originates with it, and that all cells are either formed from a nucleus of this kind, or by the division of a thin membrane in the inte- rior of the cell, which represents the nucleus, and is called a " primordial utricle." When the cells of plants have thus originated, they either remain free or only slightly adherent to each other, or they press upon each other, assuming a variety of shapes ; they then form what is called a " tissue." When cells are equally pressed on all sides, they form twelve-sided figures, which, when cut through, present hexagonal spaces. This may be seen in the pith of most plants, more especially the common elder, which is seen at figure 2 of plate 1. Transverse slices of the stems of any kind of plant from the garden may be made by a razor, or sharp penknife, and will afford interesting objects for the Microscope. Cells, during their growth, assume a variety of shapes, and the tissues which they form are named accordingly. Two examples of such cells will be seen in figures 243 and 244 in plate 8, where the first represent cells from the hard shell of a plum stone, and the second the thin cells from the out- side of the seed of the guelder rose. Sometimes the cells are very much elongated, or they unite together to form an elongated tube ; the tissue thus formed is 32 A HALF-HOUR WITH THE called " vascular tissue ;" but where the cells retain their primitive form, it is called " cellular tissue." A very interesting form of the latter is the " stellate" tissue found in most water plants, and especially regularly developed in the common rush, a represen- tation of which is given in figure 3 plate 1. The object of this tissue is, evidently, to allow of the existence of a large quantity of air in the spaces between the cells ; by which means the stem of the plant is lightened, and it is better adapted for growth in water. If the leaf of any plant is examined, it will be found that on the external surface there is a thin layer, called, after the thin external membrane in animals, the " epidermis." This layer is composed of very minute cells — smaller than those in other parts of the plant, and when placed under the Microscope, presents a variety of forms of cellular tissue. The form of epidermal cells from various plants is seen in figure 42 and the following figures in plate 2. There is found in this layer a peculiar organ which exists on the outside of all parts of plants, and which demands attention. In the midst of the tissue, at very varying distances, are placed little openings, having a semilunar cell on each side. These openings are called " sto- mates," and can be well seen in the leaf of the hyacinth, which is shown in figure 42, where the cells of the epidermis are transparent ; but the little cells which form the stomate are filled with green colouring-matter. The stomates vary very much in size and in numbers. They are found in larger numbers on the lower than on the upper side of leaves. In the common water-cress they are very small, as seen in figure 43, plate 2, and the cells of the epidermis are sinuous. The sto- mates are found on all plants having an epidermis. PLATE *^. 29 a -ii ' '^'i'S'. > il ^1 r'Z S S J J -* > ^ * J ^ . wo^; •M Uw *S U'k a B ^9 SJ"^\ '" ^ ^ ^^ 1 |;:^;:$^?^^^:^^M^iM>^V'^ ■ ^ ^/ ^ •jS-fl ^'MiM ^ J./ ■I, _ ^^ a $ ^ IS f s 'i£fen^":trt i= "yvnve?* -in^i MICROSCOPE IN THE GARDEN. 33 In figures 44 and 46 tliey are represented from the wheat and the aloe. In the latter plant the cells of the cuticle are very much thickened. They can also be seen on the cuticle of the fruit, as shown from the holly in figure 241, plate 8, and also on the organs and petals. These form a beautiful object under the Microscope. The petal of the common scarlet geranium {Pelargonium) affords a beautiful instance of the way in which the cells of plants become marked, by their pecu- liar method of growth. This is illustrated in the cells of the common red-flowered geranium at figure 45, in plate 2. The vascular tissue of plants is either plain or marked in its interior. If we examine the ribs of leaves, the green stems of plants, or a longitudinal section of wood, elongated fibres, lying side by side, are observed, as is seen in the case of the elder, at figure 53, plate 2. This is what is called " lig- neous" or "woody" tissue, and the greater part of the w^ood and solid parts of plants are com- posed of this tissue. Such tissue is seen upon the shoots of the young v^ine in figure 249, plate 8. The fibres mostly lie in bundles, and are divided from each other by cellular tissue. This latter, in the woody stems of trees, constitutes the " medullary rays," which are seen in transverse sections of stems, extending from the pith to the bark. The difference observable in the distribution of the woody fibres and the medullary rays renders the examination of transverse sections of the stems of plants a subject ot much interest ; figure 54 and the following figures in plate 3, present the appearances of thin sections of various kinds of wood (figures 54, 55, 5Q, 51, plate 3). In the transverse sections of stems of most plants, large open tubes are observed. This is seen la 34 A HALF-HOUR WITH THE the case of the oak, figured at figure 55, plate 3, These are called " ducts." Such ducts may be well observed in the transverse section of the common radish, as seen at figure 51, plate 2, and in other roots. These ducts are often marked by pores, or dots, and are hence called " dotted ducts." These dots are the result of deposits in the interior of the tube of which the duct is formed, and a great variety of such markings are found in the interior of vascular tissue. One of the most common forms of marked vascular tissue is that which is called glandular woody tissue, of which a figure is given at 54, plate 3. This kind of tissue is found in all plants belonging to the cone-bearing, or fir tribe of plants. In order to discover it, recourse need not be had to the garden for growing plants, as every piece of furniture made of deal wood will afford a ready means of obtaining a specimen. All that is necessary to observe the little round disks with a black dot in the middle is to make a thin longitudinal section of a piece of deal, and jDlace it under a half or quarter-inch object-glass, when they will be readily apparent. The application of a drop of water on the slide, or immersing them in Canada balsam, will bring out their structure better. If we take the leaf-stalk of a strawberry, or of garden rhubarb, and make a transverse section all round, nearly to the centre of the stalk, the lower part will at last break off, but be still held to the upper by very delicate threads. If we examine these threads, we shall find that they are fibres which have been left by the breaking of the vessel in which they were contained : such fibres are seen at figure 48, plate 2. These vessels are called " spiral vessels," and are found in the stems and leaves of many plants. They are seen rolled up as MICROSCOPE IN THE GARDE5T. 35 found in the garden rhubarb, at figure 47, plate 2 Sometimes these vessels are found branched, as in the common chickweed, which is seen at figure 50, plate 2. This arises from two spires coming in contact with each other, and adhering. Occasioii- ally the spiral fibre breaks, or is absorbed at certain pomts, leaving .only a circular portion in the form of a ring, as seen in a vessel from the root of wheat at figure 49, plate 2. Such vessels are called "annular," and may be observed in other roots besides those of growing wheat, as in the leaves of the garden rhubarb. A modification of this kind of tissue is seen in the stems and roots of ferns, in which the vessel assumes a many-sided form. This kind of tissue is called " scalariform," or ladder-like, and is seen in figure 52, plate 2 Sometimes the spiral fibre is free. This is repre- sented at figure 250, plate 8, from the testa of the seed of the wild sage. The bark as well as the wood of trees affords the same appearance under the I\Iicroscope. If a piece of the bark of any plant be examined by means of a very thin transparent section, and placed upon a shde, and put under an inch or a half-inch object- glass, the structure of the bark may be easily seen. On the outside of all is the cuticle, or epidermis, and under this lie two layers, composed, like the cuticle, of cellular tissue; but the inner layer, before we come to the wood of the stem, is com- posed of woody tissue. The cellular layer, next the woody one, is often developed to a very great extent, and then constitutes what we know by the name of cork. The bark from which corks are made is obtained from an oak tree which grows in the Levant. If we make a very thin section of a cork, Its cellular structure can be easily made cut. The cells are almost cubical, and when submitted to tlia 36 A IIALF-HOUE WITH THE action of a little solution of caustic potash, they may frequently he seen to be slightly pitted. This is represented from cork in figure 59, plate 3. Many of the structures which are described above may be seen in common coal ; thus proving most satisfactorily that this substance has been formed from a decayed vegetation. A transverse and a longitudinal section of coal is shown at figures 60 and 61, plate 3. The examination of coal, how- ever, is by no means an easy task, and the hands and fingers may be made very black, and the ]\Iicroscope very dirty, without any evident struc- ture being made out. Some kinds of coal are much better adapted for this purpose than others. Sections may be made by grinding, or coal may be submitted to the action of nitric acid till it is sufficiently soft to be cut. The amateur will not find it easy work to make sections of coal ; but should he wish to try, he may fasten a piece on to a slip of glass with Canada balsam, and when it has become firmly fixed, he may rub it down on a fine stone till it is sufficiently thin to allow its structure to be seen under the Microscope. Coal presents both vascular and cellular tissue. The vascular tissue is, for the most part, of the glandular woody kind; thus leading to the inference that the greater portion of the vegetation that supplied the coal-beds belonged to the family of the firs. The external forms of the tissues of plants having been examined, we are now prepared to regard their contents. In the interior of the cells forming the roots and the growing parts of plants will be observed a number of minute grains, generally of a roundish form. If we make a thin slice of a potato, these granules may be very ob- viously seen, lying in the interior of the cells of whi-ch the potato is composed, as seen at figure 64, 1 MICHOSCOPE I^' THE GARDEN. 37 plate 3. If we now take a drop of the solution of iodine, and apply it to these cells full of granular contents, we shall find that the granules assume a deep-blue colour. This is the proof that they are starch ; and as far as we at present know, no other substance but starch has the power of assuming this beautiful blue colour under the influence of iodine. We have thus a ready means at all times of distinguishing starch. The grains of starch are of various sizes and shapes. The starch of the flour of wheat has a round form, and varies in size j that of the oat is characterized by the small granules of starch adhering together in globular shapes. When these globules are broken up, the grains appear very irregular. Grains of wheat starch and oat starch are seen in figures 62 and 63, plate 3. In the arrow-root called " Tons les Mois," the grains of starch are the largest known, and, like those of the potato, they look as if com- posed of a series of plates laid one upon the other, gradually becoming smaller to the top. This is seen at figure 65, plate 3. These lines do not, however, indicate a series of plates, but appear more like a series of contractions of a hollow vesicle or bag. This vesicular a2:>pearance of starch may be made apparent by gently heating it, after moistening, over a spirit-lamp on a glass slide, or by dropping on it a drop of strong sulj)huric acid. This action of the starch-granule appears to be due to the fact that the starch is converted into gum by the action of the heat on the sulphuric acid. Sago and tapioca are almost entirely composed of starch, and may be easily examined under the Microscope. Granules of sago are represented in figure 67, and those of tapioca at figure 68 ; they are readily distinguished by their size. The starch granules are insoluble in water, but they are easily diffused ^ 38 A. HALF-HOUR WITH THE throngli it ; so that bv washing any vegetable tissue containing starch, with water, and pouring it oft and allowing it to stand, the starch falls to the bottom. This may be done by bruising the vege- table tissue in a mortar, and then throwing it into cold w^ater. The tissue falls to the bottom, and the starch is thus suspended in the water. In this way the various kinds of starches may be procured for microscopical examination. The granules of starch have frequently a little black irregular spot in their centre. In the starch of Indian corn it assumes the form of a cross, which is seen at figure 66, plate 3. Starch is a good object for the use of the polarizing apparatus, which can be applied to most compound Microscopes. The grains of starch, under the influence of polarized light, become coloured in a beautiful and peculiar manner, permitting of great variation, as in the case of all polarized objects. If we take a little of the white juice from the common dandelion, and put it under the Micro- scope, we shall often see, besides the globules of caoutchouc which make the juice milky, crystals of various forms. Such crystals are called by the botanist " raphides," — signifying their needle-like form. They arise from the formation and accu- mulation of insoluble salts in the fluids of the plant. They are seen in various plants, and under very diffe-rent circumstances. Beautiful needle-like crys- tals can be seen in the juice of the common hyacinth, represented at figure 69 ; the juice may be ob- tained by pressing. A question has been raised as to whether they are always formed in the cell. They are mostly found lying in the cell, as in the leaves of the common aloe, seen at figure 70, plate 3 : they may also be found in the tissues of the com- mon squill, and in the root of the iris. If a thin :iricRoscoPE ix the garden. 39 section of the brown outer coat of the common onion is made, small prismatic crystals are observed. These are represented at iigiire 72, plate 3. Some- times several of these crystals unite together around a central mass, forming a stellate body. These bodies have been called " crystal glands," but they have no glandular properties. They may be seen in the root and leaf-stalk of common rhubarb, and may be easily observed in a bit of rhubarb from a spring tart. From such a source, the drawing was made at figure 71. These crystals are mostly formed of oxalate of lime. They are constantly found in plants producing oxalic acid. The gritty nature of rhubarb root arises from the presence of oxalate of lime. Sometimes the oxalate of lime assumes a round dish-like form. Such forms are seen in plants belonging to the cactus family. A circular crystalline mass, as seen in a common cactus, is represented at figure 73. Other substances, besides oxalate of lime, are found crystallized in the interior and on the surface of plants. Crystals of sulphate of lime have been found in the interior of cycadaceous plants. Car- bonate of lime is found in crystals on the surface of some species of Chara, or stonewort. There is a shrub not uncommon in gardens, known by the name of Deutzia scabra, on the under surface of the leaves of which there are beautiful stellate crystals of silica. The best way of seeing these is to put the leaf under the Microscope, and to examine it by the aid of reflected light. Sugar and honey assume a crystalline form, and may be known by the shape of their crystals. At figure 238, plate 8, a crystal of honey is repre- sented ; it is thinner and smaller than the crystal of cane sugar represented at figure 239. Honey is sometimes adulterated with sugar. Under these 40 A HALF-HOUR WITH THE circumstances the sugar crystal loses its definite outline, and assumes the form seen at figure 240. The external surface of the parts of all plants will aflTord a rich field of amusement and instruc- tion to the microscopic observer. The cuticle, or epidermis, of which we have before spoken, has a very varied structure, and contains the little open- ings (stomates) before described. The cuticle, which, in a large number of cases, is smooth, becomes elevated in some instances, and forms a series of projections, which, according to their form, are called " papillae," " warts," " hairs," " glands," and " prickles." The papillae are slight elevations, con- sisting of one, two, or more cells ; the warts are larger and harder ; whilst the hairs are long, the glands contain a secretion, and the prickles are hard and sharp. For examining the form and growth of these hairs, the flowers of the common pansy (heart's-ease) afford a good object. Some of the projections are merely papillae, as in the case of the kind of rudimentary hair rejDresented in figure 75, plate 3 j others are found longer, and more like hairs, as seen in figure 76; whilst others are long, and, the sides of the hair having contracted, they assume the appearance of a knotted stick, as seen in the hair from the throat of the flower of the pansy, at figure 78. The family of grasses, wheat, barley, oats, and other forms, are favourable sub- jects for the examination of simple hairs, or hairs composed of a single elongated cell. At figure 74, a single hair is given from a common grass. All that is necessary to be done, in order to see these hairs, is to take any part of the plant where they are present, and to slice off a small portion with a sharp penknife or razor, and place it under the Microscope. They may be either examined dry, or a little water may be added, and a piece of thin MICROSCOPE O THE GARDEN. 41 glass placed over them on the slide. Hairs are frequently formed of several cells. On the white dead-nettle the hairs are composed of two cells, as seen in figure 79 a. The nucleus, or cytoblast, is often seen in these, and is represented in figures 76, 77, and 79, plate 3. On the common groundsel hairs may be seen, composed of several cells, each cell containing a nucleus, as at figure 796. Hairs like a string of beads are found on the pimpernel and sow-thistle, which last will be found m ficrure 80, plate 3. Occasionally haii^ become branched. Thus, on the leaf of the common chrysanthemum the hairs present the form of the letter T. This hair is represented at figure 82, On the under-surface of the leaves of the common hollyhock hairs are seen with several branches, giving them a stellated appearance, as seen at figure 84. The common lavender is covered with st'ellate hairs, as seen at figure 85a. These hairs may be examined as opaque or transparent objects, when immersed in a little glycerine. The hair of the tobacco plant presents a peculiar knobbed appearance. The presence of these hairs is a test of the purity of tobacco. It is shown in fic^ure 81. The verbena has rosette -shaped hairs° as in figure 83. Sometimes hairs are covered over with little dots, which are supposed to be deposited after the growth of the cells of the hair. Such hairs may be seen in the common verbena, and are represented at figure 856. Hairs are sometimes loose and long, as in the white poplar, seen at figure 86. Occasionally an elevation, consisting of several cells, is formed at the base of a hair. These are shown in figure 87. When these cells contain a poisonous secretion, which is transmitted along the tube of the hair, the hair is called a glandular hair, or sting. Such aro 42 A HALF-HOUR WITH THE the hairs of the common stinging-nettle, represented at tignre B>Sa. The hairs constituting the down or " pappus " of compositoiis plants assume a variety of forms The seed or fruit of the common groundsel has a beau- tiful crown, given at figure 245, in plate 8. The papiDus of the dandelion appears notched, as seen at figure 2i6. The burdock has a cottony hair, while the goatsbeard is like a feather,-both of which are represented respectively in fi^rures 2i7 and 248. ° If a hair is examined in its growing state, with an object-glass of one quarter of an inch focus a movement of the particles in its interior is often observed. This is easily seen in the hairs around tne stamens of the common Spiderwort (Trades- canha Virginica). Such movements are very com- mon in the cells of water plants. One of those most commonly cultivated in aquavivaria at the present day, the Valisneria sjjiralis, affords the best example of this interesting phenomenon. In order to observe this movement, a growing leaf of the valisneria should be taken, and a longitudinal slice should be removed from its surface, by means of a sharp penknife or razor. The slice, or the sliced part left on the leaf, should now be put on a slide a drop or two of water added, and covered with a thin piece of glass, when, after a little time, espe- cially m a warm room, the movement will be ob- served. This movement takes place in the little particles around the sides of the cells represented m figure 88b, plate 3. It may also be seen in the leaves of the new water-weed (Anacharis ulsmastrum), the frogbit, the rootlets of wheat in the family of charas, and in the cells of many other water plants. In examining some species of Chara the external bark, or rind, should be removed from MICBOSCOPE IN THE GARDEN. 43 tie cells, or the movements will not be seen. This movement seems dependent on the internal proto- plasmic matter, or " primordial utricle," which ia contained in many cells, and which, in these cases, is spread over the interior of the cell. It is, how- ever, capable of contraction, and when the plants are exposed to cold, the utricles contract and pre- vent the movement of the contents in the interior. It is, apparently, the extension of this substance beyond the walls of the cell which constitutes the little hairlike organs called "cilia," which are con- stantly moving, and by the aid of which the spores of some plants effect rajDid movements. Such orgfans are found in the Pandorina Morum and Volvox glohator, moveable plants represented at figures 13 and 14, plate 1. The effect of these cilia in producing the movements of plants is well seen in the Volvox glohator, which, on account of its rapid movements, was at one time regarded as an anwialcule, but it is now regarded as a plant. Cilia are, however, more frequently met with in the animal kingdom. They are seen in the drawing of Flumatella repens, at a, in figure 163 of plate 6. Amongst the parts of plants w^hich can alone be investigated by the Microscope are the stamens. These organs are situated in the flower, between the petals and the pistil, and usually consist of a filament, or stalk, with a knob or anther at its top. If the anther is examined, it will usually be found to consist of two separate valves, or cases, in each of w^hich is contained a quantity of powder, or dust, called " pollen." The walls of these valves are worth careful examination under the Microscope, on account of the beautifully-marked cellular tissue of which their inner walls consist. The cells of this tissue contain in their interior spiral fibres similar to those which have been described as present in 44 A HALE-HOUR WITH THE certain forms of vascular tissue. In tiie antliers of the common fui^ze the fibres are well marked, and are represented in figure 118, plate 5 ; in the common hyacinth they are larger, and frequently present, in their intercellular spaces, bundles of raphides, as seen at Figure 119. In the white dead-nettle the fibre is irregularly deposited, as at figure 120, In the anthers of the narcissus, given at figure 121, the cells are almost vascular in their structure, and present the same appearance as those described under the head of annular ducts. The reader should compare figure 121, plate 5, with figure 49, plate 2. In the crown imperial the fibres of the cells radiate from a central point in a stellate manner, as at figure 122. When the anther-cases have been examined, a little of the dust may be shaken on to a slide, and examined as an opaque or a transparent object. Each species of plant produces its own peculiar form of pollen. These little grains are actual cells. They are the cells of plants which in their position in the anther will not grow any further. They are destined to be carried into the pistil, where, meet- ing with other cells, they furnish a stimulus to their growth, and the embryo, or young plant, is pro- duced. The history cf the development of these cells, as well as of those in the interior of the pistil, is a very interesting one, and is one of those sub- jects of investigation which has been created by the aid of the Microscope. The jDollen grains vary in size as well as form. They are frequently oval, as seen in figure 123, plate 5. In the hazel and many of the grasses they are triangular. Those from the hazel are re23resented at figure 124. In the heath they are tri-lobed, as at figure 125 ; in the dandelion, and many of the compositous order of plants, they are beautifully sculptured, as seen MICROSCOPE IN THE GAPXEN. 45 at figure 126. In the passion-flower, three rings are observed upon them, as though they had been formed with a turner's lathe — figured at 127. In the common mallow, they are covered all over with little sharp-pointed projections, like a hand-grenade. These are represented at figure 128. The micro- scopic observer should make himself acquainted with the forms of pollen grains, as, on account of their small size and lightness, they are blown about in all directions, and may be found on very dif- ferent objects from those in which they have been produced. Some absurd mistakes have been com- mitted by confounding pollen grains with other forms of organic matter. Thus, pollen grains in bread were regarded as bodies connected with the production of cholera. The pistil, which is the central organ seated in the midst of the stamens in the flower of plants, will afford a great variety of interesting points for examination with the Microscope. In the earliest stages of the growth of the pistil, thin sections of it may be made, and the position of the ovules observed. In the ovule will be found the embryo sac, a central cell, which, on being brought in contact with the pollen grain, grows into the seed. The seed contains the embryo, or young plant. In most plants this is sufi^ciently large to be seen by the naked eye ; but it may, nevertheless, be examined with advantage by a low microscopic power The seed is covered on the outside with a membrane, which is called the " testa." This membrane is often curiously marked, and the whole seed may be examined as an opaque object with the low powers of the Microscope. In order to do th>s, the light must be shut off from the mirror, and, the object being placed on the stage, a pencil of light should be thrown upon it by the aid of the ^6 A IIALF-HOUE WITH TIIF bull's-eye condenser. If a seed of the red poppy be^ now examined, it will be found to have a uniform shape, and to be reticulated on its surface as seen at figure 129, plate 5. The seed of the black mustard exhibits a surface apparently covered with a delicate network, seen at figure 130. Some seeds have deep and curved furrows on their sur- faces, such as exhibited in figure 131. The great snapdragon has a seed covered with irregular projecting ridges, having a granuled appearance represented at figure 132. The seed of the chick- weed presents a series of blunt projections, as in figure 133. In the various forms of umbel- bearing plants, the seeds adhere to the fruit, and the fruit is commonly called the "seed." Such are caraway, coriander, dill, and anise seeds. The plants of this family are very common weeds in our gardens and fields, and may be easily procured for microscopic examination. Some of these fruits are covered over with little hooks, seen at figure 134, whilst others present variously -formed ridges and furrows, which are amongst the best means lor d.^i3tingu]shing these plants the one from the other. PLATE Z ■'7 JS t ^£CC-CJr f 59 \K ,M^ -t" t^ ^i^m^! 6Z V d (9B O 73 IviSjn'WeEt so. ad nat , WYfc.Tt my Lon.l.t "R->)-ir: Fard'/Jicke, 1^60 MICROSCOPE IN THE COUNTPwY. 47 CHAPTER III. A HALF-HOUR WITH THE MICROSCOPE IN THE COUNTRY. A Co:mpouxd Microscope is not easily conveyed and put up in the fields, but tlie produce of the roads and waysides may be easily brought to the Micro- scope at home. iSTo one who has a Microscope should walk out into the country without supply- ing himself with a few small boxes, a hand- net, and three or four small bottles, in order to bring home objects for examination. The dry produce, which may be put into boxes, is of a different character from that which may be conveyed home in bottles. We shall, therefore, first direct attention to the minute forms of mosses, fungi, lichens, and ferns, which may be collected in boxes ; premising, however, that many members of these families may be found without going into the country to seek for them. The cheese in the pantry, and the decayed parts of fruits, and objects covered with mould, are good subjects for microscoj^ic examination. Amongst the minuter plants and animals whose true nature can only be detected by the Tdicroscope many are composed of a single cell, whilst others, like higher plants and animals, are formed by the union of a large number of cells. The greater proportion of the one-celled, or unicellular plants, as they are called, are found in water : but some are found on moist rocks, stones, and old walls. Amongst these there is one of exceedingly simple structure, called gory dew {Pahmlla amenta). This 48 A HALF-HOUR WITH THE plant appears as a red stain upon the surface of damp objects. If a little of this red matter is scraped off the object to which it is attached, and placed under the JMicroscope, it will be found to consist of a number of separate minute cells, as represented at figure 89, plate 4. This plant belongs to the same family as the red-snow plant, and there are a number of forms of these minute organisms, which, on account of their rapid growth and red colour, have given rise to alarming appre- hensions, in former times, when their true nature was imperfectly understood. One of them attacks bread, and gives to it the appearance of having been dipped in blood. They also attack potatoes. Of the same simple structure, but not having a red colour, is the yeast-plant, or fungus, shown at figure 90, i^late 4. This plant abounds in yeast, and may also be found in porter and ale. If vinegar is allowed to stand for some time, a minute plant is developed, called the vinegar- plant. In its earlier stages of growth it exhibits elongated cells, looking like broken pieces of thread, seen at figure 91. Threads more fully developed are often seen in decomposing fluids, and upon the surface of decomposing animal and vegetable substances ; such is the so-called cholera- fungus, which may be obtained by exposing damp slides to the air. They are shown at figure 92. Such plant-like threads can be collected from the air in damjj and unwholesome cellars and rooms, and were at one time supposed to be connected with the production of that fearful disease, the cholera. It has been rendered, however, exceed- ingly probable that all these appearances are but different forms of the fungus which produces common mould, and which is known by the name of Fenicillium glaucum. This fungus is represented MICROSCOPE IN THE COUNTRY. 49 at figure 95. It may be found on the surface of preserves and jellies, and consists of a mass of fila- ments or threads serving as its base, from the surface of which individual filaments rise up, bear- ing a number of minute cells, which are the spores, or reproductive organs. These are seen at figure 96. Plants such as these, and belonging to the family of fungi, are found everywhere on the leaves of plants in the summer and autumn, forming irre- gular spots, of a yellow, red, or black colour. If such leaves are brought home and placed under the Microscope, they present a never-failing source of interest. The red appearance on the leaves of wheat, called the rust, is due to one of these fungi, seen at figure 93, plate 4. This appears to be an early stage of the fungus, which produces what is called mildew, and is represented at figure 94. These fungi are so common on the wheat-plant that their spores mingle with the seeds when ground into flour, and can be found, when care- fully sought for, in almost every piece of bread that is examined under the Microscope. Mouldy grapes, pears, apples, and other fruits, present fungi, having the same general form as that of common mould. Such a fungus is the Botrytis of mouldy grapes seen at figure 96. Mouldy bread also pre- sents a fungus of this kind. This species is called Mucor mucedo, and is represented at figure 97. Its spores are arranged in a globular form. A fungus not unlike the last has been described as srowintr in the human ear, and is figured at 98. The leaves of the common bramble present a fungus in w^hich the spores are arranged on a more dense and elongated head. This is called Fhragmidium hulhosam, and is represented at figure 99. Tiie Oidlum which attends the bli'dit of the vine, bttJj 50 A HALF-HOUR WITH TIIK at figure 100, and the Botrytis which aocompauici the potato disease, figure 101, are other and in- teresting forms of these minute parasites. Thf common pea is subject to a blight which is aossesses two cilia. But the most remarkable of this kind of moving plant is the Volvox glohator, represented in figure 14 of the same plate. This beautiful moving plant was at one time thought to be an animalcule, but it is now inCKOSCOPE AT THE POND-SIDE. ^1 rcgariled as a true plant. It consists of a lars^o number of spores, or cells, each having two ciiiji, and connected together by a delicate network of threads. In the interior of this moving sphere are seen smaller globular masses, of a dark-gTeen colour, which are the young of the volvox, which have not yet developed the network, by means of which their spores are separated, and their ciliated ends pre- sented to the water, and by means of which their movements are effected. Another form which is now regarded as a loco- motive plant is the Euglena viridis, seen at figure 15, plate 1. It is often found in prodigious num- bers, giving to water the appearance of green-pea soup. When placed under the IMicroscope, it fre- quently presents a red sj)eck, or point, at one end, and an elongated tail at the other. The red spot has been regarded as an eye ; but if it is watched, it will be found the red colour will often extend from the red spot to the rest of the body ; and it is probable that the i"ed colour is only a change in the condition of the chloro})hyle contained in its interior. Amongst this class of plants it is not unfrequent for the chlorophyle to assume a red colour at certain stages of its growth. The transition from the filamentous to the mem- branous form of these plants is well seen in the species of Ulva. These are found in both fresh and sea water. In the early stages of its growth, the ulva presents the filamentous form of a conferva, as seen at a, in figure 26, plate 2. Gradually the cells of the filament split up into two or three seams (6) ; and this goes on till at last a broad fiat membrane is produced (c). If the plants of our fresh waters are interesting, not less so are the animalcules ; for, just as we have one -celled plants so we have one-celled ani- 62 A HALF-HOUR WITH THE mals, and it was only by the aid of the Microscope that they were discovered and can be examined. AYherever the above jjlants are found, there will also be discovered animals to feed upon them. The animal is distinguished from the plant by its feed- ing on plants, whilst the latter feed on inorganic substances. There is considerable difficulty in at once dis- tinguishing between tL® lowest forms of animals and plants. Although the animal generally pos^ sesses a mouth, and a stomach in which to digest its vegetable food, there are some forms of anima' life so simple as not to possess either of these organs. In the sediment from ponds and rivers there will frequently be found small irregular masses of living, moving matter. If these are watched, they will be found to move about and -jhange their form constantly. As they press them- fielves slowly along, small portions of vegetable matter, or occasionally a diatom, mix, apparently, with their substance. Cells are produced in their interior, which bud off from the parent, and lead the same life. These creatures are called amsebas, and are represented in our first plate, figure 16. Although they have no mouth or stomach, ihey are referred to the animal kingdom. They appear to consist entirely of the formative matter found in the interior of all cells called moto planes or sarcode without any cell- wall. If we suppose an amseba to assume the form of a disk, and to send forth tentacles ^r minute elongated processes from all sides, we should have the sun animalcule {Actinophrys Sol), which is represented at figure 17, plate 1. This curious creature has the power, apparently, of suddenly contracting its tentacles, and thus leaping about in the water. It can also contract its tentacles over particles of starch a* id P7 ATTT ^ SI w, /25 ._ /2t /27 ii^^lB® ^^2 i5i 1^ ^fXvuV fr ^"^'i-- -^-i-''^S F'^M^i Imter. ■".(:« £0 &,i. i:^ ,S' lEI La&dgt: ^Rabert Bar dwicke. 1860 MICROSCOPE AT THE POXD SIDE. f;3 animalcules, and press them into the fleshy sub- stance in its centre. This is undoubtedly an animal, but it has no mouth or stomach. A large number of such forms present themselves under the Micro- scope. Some of them are covered with an external envelope, which they make artificially, by attachiug small stones and other substances to their external surface, as in the case of the DifflugicB, seen at figure 18, plate 1 ; oi they may form a regular case, or carapace, of cellulose, as in Arcella, repre- sented at figure 19. We shall meet again with forms resembling these when we take our Micro- scope to the sea-side. One of the most common animalcules met Avith in fresh water, and whose presence can easily be insured by steeping a few stalks of hay in a glass of water, is tlie bell-shaped animalcule. These fc;nimalcules, which are called Vorticella, are of various sizes. Some are so large that their presence can easily be detected by tbe naked eye, whilst others require the highest powers of the Micro- scope. They are all distinguished by having a little cup-shaped body, which is placed upon a long stalk, figured at 40, in our second plate. The stalk has the peculiar power of contracting in a spiral manner, which the creature does when anything disturbs it in the slightest manner. In some species these stalks are branched, so that himdreds of these creatures are found on a single stem, forming an exceedingly beautiful object with the Microscope. The stalks of these compound vorticellse are con- tracted together, so that a large mass, expanding over the whole field of the Microscope, suddenly disappears, and, " like the baseless fabric of a vision, leave not a wreck behind." A little patience, however, and the fearful creatures will once more be seen to expand themselves in all their beaiuy. G4 A HALF-HOUR WITH THE The moutli of their little cup is siuTOunded by cilia, which are in constant movement ; and when ex- amined minutely, they will be found to possess two apertures, through one of which currents of water pass into the body, and from the other pass out. Not unfrequently the cup breaks ofi its stalk. It then contracts its mouth, and proceeds to roll about free in the water. Many other curious changes in form and condition have been observed in these wonderful bell-shaped animalcules. If, now, we go to a very dirty pond indeed, into which cesspools are emptied, and dead dogs and cats are thrown, we shall find a5' 210 TuEtn Vif; -t so.sa ii-it. London- Robert Ear" i- o '^^( a- MICROSCOPE IN-DOOrvS. 79 scope, the pulpy portions will present a dark ap- pearance in the centre, as seen at a. The hairs of animals offer a great variety in the disposition of the cells of which they are composed. The hairs of the mouse present a series of dark partitions running across the hair between the cells. In the younger hairs, these partitions are single, as repre- sented at a in figure 185, plate 7 ; whilst in the older ones they appear double, as seen at h. The hairs from the ear of the mouse present these dark partitions very distinctly, shown at d. Such hairs stand intermediate between true hair, a section of which is seen at c, and wool. A piece of flannel or blanket will afford a good illustration of the latter. This is figured at 235 in the 8th plate. In this case it will be seen that the scales, or cells, of thtj cortical part, project beyond the surface, and render the wool rough. This roughness of the outside is supposed to render such hairs fitted to be used in the process of felting ; the rough sides of the hairs adhering together. The chemical composition of the hair has also something to do with this pro- cess. Human and other smooth hairs, will not felt. The fibres of plants used in weaving may be conveniently compared with hairs derived from the animal kingdom. The woody fibre of the flax may be obtained from a linen handkerchief A linen fibre is represented at h in figure 234, plate 8. The apparent knots in the fibre arise from injury in the uses to which the fabric has been applied. The original fibres have no such fractures, as shown at a, and are perfectly smooth. So are the fibres of silk, represented at figure 236. Cotton-wool is produced from the inner surface of the pod, or fruit of the cotton-plant, and is figured at figure 237. It becomes twisted during its growth, and although 80 A. HALF-HOUR WITH THE not SO strong as linen or silk, its irregular surfaces permit its being spun into a strong yarn, from which all cotton fabrics are made. The young microscopist should make himself acquainted with the forms of these various fibres ; as, from their being so constantly present in rooms where the Microscope is used, and occasionally employed in cleaning the apparatus, they often present them- selves as foreign substances, among other objects that are beins: examined. It is also interesting, and sometimes of import- ance, to be able to ascertain of what material a fabric may be composed. Thus by means of the Microscope, and that alone, we know certainly that the cere-cloths in which Egyptian mummies are wrapped is a linen fabric, whilst the similar invest- ment of Peruvian mummies is cotton. The hair of the bat, represented at figure 186, plate 7, presents a singular instance of the projection of the scales, or cells, in a regular form. Hairs are not often perfectly round ; — in the peccary they are oval, as seen in figure 187, plate 7. If a transverse section of this hair is examined, it will be found that the cortical substance projects completely into the pulpy part of the hair in several places, so as to break up the pulp into several separate sections. In some cases it is not easy to distinguish between outside and inside structure, as seen in the hair of the musk-deer, in which the whole is found to consist of a mass of hexasfonal cellular tissue, similar to that seen in the pith of plants. This hair is shown in plate 7, figure 188. Insects are frequently covered with hairs, espe- cially in their larva, or caterpillar state. These hairs when stiff and sharp, penetrate the skin, and produce irritation there. This is the case with the large tiger caterpillar. The hairs of this cater- MICROSCOPE IN-DOORS. 81 pillar are furnished with a series of barbs, which, when they once penetrate the skin, are not easily removed, as seen in figure 189, plate 7. Spiders are frequently covered with hairs, some of which are branched, as at a in figure 190; others present a spiral appearance, seen at h ; whilst, again, others offer a series of small bristle- like hairs running down each side of the primitive hair, which will be seen at c. Many of the Crustacea have hairs upon their shells. Those upon the flabellum of the common crab have minute bristles on one side of the parent stalk, so as to form a little comb, with which to brush off the impurities from its branchiae. This structure is seen at figure 191 in plate 7. A live crab from the aquarium may be watched for the purpose of observing these cleanly movements. The study of the uses of the epidermal ap- pendages is one full of interest, as in no one set of structures do we find a greater variety of adaptations of a common plan to the wants of the creatures in which they are found. The feathers of birds belong to the same type of structure as the hairs of animals. If the pinnae of a common goose-quill, used for a pen, are examined, the pinnules will be found to be covered with minute hooks, drawn in figures 192 and 193, plate 7. These hooks on the upper surface are so arranged that they catch the nearly plain and slightly toothed pinnules on the lower side. The down from the feathers of the swan, with which pillows and beds are stufied, is also a beau- tiful object, and its microscopic structure will at once reveal the cause of its lightness, softness, and warmth. This is seen at figure 194, in the 7th plate. Amongst the creatures which domesticate with a 82 A HALF- HOUR WTTH THE US are certain insects which are more frequently discovered than acknowledged. However dis- agreeable their presence may be, they become interesting objects for microscopic investigations, and are not less calculated to excite our admira- tion than creatures more ceremoniously treated. We first call attention to the common flea {Pulex irritans). This beautiful insect belongs to a large family, each species of which has its peculiar habitat in the epidermal appendages of some of the higher animals. The head of the human flea may be taken as the type of the family. This is represented with great accuracy at figure 195, in plate 7. It is furnished with antennae, mandibles, and a pair of lancet-shaped jaws, with which it makes little wounds in the skin, and into which it pours the irritating secretion which renders its bite a source of annoyance. Its eye, large hind legs, and orna- mental saddle on its back, are all deserving of attention. Let us now seek another too common inhabitant of London houses, the bed-bug (Cimex lectulariu^), and, having decapitated him, submit his head to a low power. He, too, is a biting creature ; and you will observe, as drawn in figure 196, that his jaws are finer than those of the flea, and are like a pair of excessively fine sharp hairs ; they are inclosed in a sheath, from whence they are projected when used. In the same sheath is the tongue, which performs the double ofiice of depositing in the wound an acrid and irritating secretion and suck- ing up the blood of its victim. The antenna and eyes of the bug are also worthy of examination. From the latter will be found projecting minute hairs. A still more despised animal may now be sought (Fediculus). It also belongs to a large family, and LIICROSCOPE 1N-D00R3. g3 each mammal and bird seems to be attended with its peculiar louse. Two species are found in dirty ^nd diseased conditions of the human body. Dis- gusting as connected with want of cleanliness, they are, nevertheless, perfectly harmless. The head and mouth, drawn in figure 198, indicate that these creatures are adapted to live on the secretions of the skin. The above animals all belong to the much larger group of creatures adapted to live as parasites upon other animals. The head of the common gnat, figured at 199, in plate 7, may be now examined for the sake of comparison. In this creature, the eye of the insect may be studied. It is what is called a compound eye, and is composed of innumerable small lenses ; each one of which is connected with a twig of the optic nerve, and capable of receiving impressions from external objects. The little lenses terminate on the convex surface of the eye, presenting an immense number of hexasfonal facets. These are seen at figure 210, plate 7. In the common house-fly, there are said to be 4,000 of these facets; and in the cabbage-butterfly 17,000. The antennae of the gnat are very beautiful ; and, in fact, these organs in insects aSbrd an endless variety of forms. At their base, in the gnat, is seen a round process on which these are seated, and it has been supposed that they are organs of hearing. Whether they are organs of hearing or not, it is very certain that they are organs of touch, and the creature is very susceptible of the slightest stimulus applied to them. The head of the honey-bee may be now examined ; and if a careful dissection is made of its mouth, a marvellous apparatus is unfolded to view, which is exhibited in figure 201, plate 7. At the base is seated the so-called mentum, and on each side ara Q ^ 84 A HALF-HOUR WITH THE placed the mandibles ; above these, and longer, are the maxilloB, and on each side of the prolonged central organ, called the tongue, are placed the labial palpi. The tongue can be retracted between the palpi a& into a sheath. It is marked by a series of annular divisions, and, by a high power,^ will be seen to be covered over with hairs. This is the organ by means of which the bee " gathers honey all the day." Whilst examining the bee, its sting may be taken out and placed under a low power, when it will be found to present the appearance of a pair of spears set with recurved barbs, which run part of the way down one side of each half of the sting. This is seen in the 7th plate, figure 200. Each of these spears is grooved on the opposite side, the two, when united, forming a canal, down which are poured the contents of the poison-bag, producing the painful effects of wounds from these instru- ments. To return to the head and mouth of insects : — The tongue of the bee may now be compared with the same organ in the butterflies, which in them assumes the form of a proboscis, and is called the haustellum, seen at figure 203, plate 7. This instrument is coiled up when the insect is at rest, and is the organ by means of which the creature sucks up its nutriment from the flower. It has a series of lines running across it. If the head of the common blowfly be now examined, it will be seen that the tongue, instead of being elongated as in the latter instances, is expanded laterally. This is represented in figure 202, plate 7. It is a very beautiful object, and when viewed by transmitted light, a series of spiral bands are observed to wind across each half of the tongue. » MICROSCOPE IN-DOORS. So The head of the common garden spider {Eperia diadema) presents an interesting development of the mandibles. These organs are in pairs ; each mandible consists of two joints : one is small, sharp, and hooked ; whilst the other is large and short, and contains within it a bag, or poison- gland ; so that when the creature seizes its prey, the bag is pressed on, and a drop of the poison exudes. This organ is represent d in figure 204, plate 7. This structure is similar to what is met with in the poisonous serpents, where a poison-bag is seated at the base of a tubular tooth. The description above given is the generally received one ; but Mr. John Blackwall, our greatest authority on spiders, considers the use of the term " mandibles " to parts entirely without the mouth objectionable ; he has accordingly bestowed the name of "falces" upon them. Some carefully- conducted and interesting experiments of his on their so-called poisonous secretion seem to throw great doubts on the propriety of regarding them in this light, and he has been led to consider that the purposes of it may rather be to deaden pain and still the struggles of a captured animal, as chloro- form is given previous to and during operations on human beings. The head of the spider affords also a good example of what are called simple eyes. Besides the compound ones before mentioned, insects have also these simple eyes — drawn at figure 208, plate 7. They consist of a single lens, as seen at a, and are placed in various positions in the heads of spiders. The skin of the common garden spider is covered with hairs. These appear to surmount a series of concentric plates, seen at figure 209, plate 7 . They vary in form in different species of spider ; 86 A HALF-HOUE WITH THE and the skin of all should be examined for the purpose of observing these differences. The web of the spider should also be examined. The cords of these beautiful structures, which run from the centre to the circumference of the web, are plain, as seen at figure 214 ; whilst those which form the concentric lines are beaded with drops of a glutinous substance. It is by means of this adhe- sive matter that the webs are held tofrether. Nor should the microscopist neglect examining the spinnarets of the spider, by which these beautiful threads are elaborated. The breathing organs of insects are well de- ser^dng attention. Their bodies are perforated at the sides, and the openings thus formed, called spiracles, lead into tubes which are branched, and are called tracliece. These air-tubes are composed of a delicate membrane, which is supported on a series of delicate rings, which are easily traced into the more minute branches. They are well seen in the larvae of most of the lepidopterous insects, and represented from a caterpillar in figure 222, plate 8. The spiracle is not an open hole. In the common house-fly, seen at figure 212, plate 7, and the water-beetle (JJyticus), in figure 213, it is covered over with irregular branched processes from the sides of the opening. The object of this obstruction is probably to prevent particles of dust, and other foreign substances, from entering the air-passages, and thus c}>oking the animal. The legs of insU-ti A^ill afford an almost un- limited supply of objects for examination. The spoilt specimens of a summer's capture may well ♦upply materials for a winter's examination. The >3gs of insects are composed generally of five parts, jointed together. The lowest of these is called the tarsus, or foot. It is variously formed to adapt it PLATK b 218 wmm lui'Lr. 7/031 EC adnal. 'AT.'.-- . London : Boben "HarcIwL.iB, 1860. MICROSCOPE IX-DOORS. 87 to the locomotive habits of the insect. In th« common fly it is terminated with a pair of disks, which are covered with suckers, called ^Jw^r^Y/i. Those of the Empis, a species of fly, are drawn at figure 205, plate 7. By means of these suckers the animal is enabled to lay hold of smooth surfaces, and thus to crawl up them. They also exude a glutinous matter, which assists in this process. The same kind of arrangement is observed in the common bee, represented in figure 206. The feet are also covered with hairs, and are frequently supplied with hooked joints, which assist the animals in laying hold of rough objects where their suckers would be of no use. In the spider there are no suckers, but the hooked joints and hairs enable the creature to crawl with facility. These hooks are seen in the foot of the spider in figure 207, plate 7, In the Dyticus the fore leg is supplied with two large Ruckers, which are seen in figure 218, plate 8, besides a number of smaller ones, and a hook ; whilst the foot of the middle leg is destitute of the large suckers, as seen at figure 219. The legs of beetles are often covered with little cushion-like bodies, which undoubtedly act as suckers. These are seen at figures 215, 216, 217. The three legs often difler very much from each other, and probably perform modified functions, according to their structure. This is well seen in the legs of the whirligig-beetle (Gyrinus natator), in which the first leg, in figure 215, is very much elongated, whilst the third is broad and short, as at figure 217, and adapted for swimming, from its oar-like form. The second leg, seen at figure 216, is intermediate in form and size. As a contrast to these legs, adapted for the varied functions of the ])erfect insect, the leg of any common caterpillar may be examined j when it 1 S8 -A- HALF- HOUR WITH THE will be found to consist, at its extremity, of a little sac surmoimted with hooks. These hooks are represented in figure 223, plate 8. The wings of insects, too, are beautiful objects ; easily investigated by a low power. The nerves which run through them are supplied with tracheae, and they thus become organs of respiration. The under wing of the bee is supplied with a series of hooks, seen at figure 211, plate 7, which slide on a thickened nerve on the upper wing, marked a, and keep the wings steady during flight. The lepidopterous insects, including the butter- flies and moths, have got their name from the scales on their wings. These scales assume a wonderful variety of form, and claim a large amount of atten- tion from the microscopic observer, and cannot be neglected by the entomologist. The little blue argus butterfly has scales in tLi shape of a battledore, drawn at figure 225, plate 8, the handle being the part attached to the wing. All the scales have handles of this sort, whatever be their shape. At figure 226, a scale of ordinary sha})e is represented. Sometimes the scale is broad at the base, and pointed at top. In the meadow- brown butterfly, the point is surmounted with little clubbed projections, drawn at figure 227. Scales are found on other insects besides moths and butter- flies : thus they are found on the common gnat. These are shown at figure 228. Besides their curious forms, the scales are marked with lines which are exceedingly delicate, and require the highest powers of the Microscope to bring them out. Some of the scales are thus used as tests for the powers of the Microscope. Just as we have seen in the tongues and legs of insects, the same parts expanded or compressed according to the wants of the animal, so we find the MICROSCOPE IN-DOOEa 89 Bcales assuming various forms. The scales stand io exactly the same relation to the hairs in insects, that the scales of fishes and reptiles do to the feathers of birds and the hairs of mammals. Hair- like scales are therefore not uncommon. At figures 229 and 230, such scales are represented, and may be found on the common clothes-moth. The young microscopist, for whom our book is written, and with which we hope to make him dissatisfied, in order to facilitate his progress in natural history inquiries^, will not spend much time in making dissections. Should he wish to do so, he well find the structure of insects full of interest. He has only to open a cockroach to see how curiously their digestive apparatus is constructed. This insect has a gizzard, and at the upper part it is beset with six conical teeth, as seen at a, in figure 220, plate 8 ; these teeth, working together, reduce its food to a pultaceous mass previous to digestion. When cut open, their position and re- lations can be easily seen, as figured at 6. The gizzard of the cricket is also supplied with teeth, seen at a, figure 221 ; it has three longitudinal series of teeth, and each row in each series contains seven teeth. The family of insects to which the cricket belongs {prthopterd) affords several other instances of the same kind of structure in the gizzard. It will be interesting to compare these teeth of the insects with those of the moUusca and the wheel animalcules. We must satisfy oui^elves with having shown the student the way to cultivate a large field of interesting and instructive phenomena in the insect world, without going further into detail. The tissues or textures of which animals are built up or made may be easily procured in-doora. We have spoken of the hard parts which form the 90 A HALF-HOUR WITH THE outer skeleton of the lower animals, as tbe mol- luscs, crabs, and fishes ; the internal skeleton of the higher animals affords a not less interesting field of research. If we take a piece of bone, and having ground it so fine that we may examine it with transmitted light under the Microscope, we shall find it composed of a number of minute insect-shaped cells, surrounding an open canal, as seen at figure 232, plate 8. These cells, which are called lacuncB, and their little branches canaliculi, are modifications of the cells found in fishes' scales, and figured at 175, plate 6. These curiously-shaped cells differ in size and form in the various classes of animals belonging to the sub-kingdom Vertebrata, and thus a small por- tion of a bone will frequently serve to indicate whether an animal belonged to fishes, reptiles, birds, or mammals. This is a matter of importance to the geologist in determining the character of the inhabitants of the earth at former periods of its history. A section of whalebone is figured at 242, plate 8. The shells of eggs seems to be formed on the same general principles as other hard parts, and the tendency to the formation of cells with canaliculi may be easily observed, as in the section of a com- mon egg-shell, represented at figure 181, plate 6. The young egg-shell should be examined, a section of which is seen at 182, if the object is to study the history of the development of the shell ; and this may be compared on the one hand with the shells of the Mollusca and the Crustacea, and on the other hand with those of the scales, teeth, and bones of the vertebrate animals. Egg-shells present very different appearances. The shell of the emu, for instance, exhibits a series of dark triangular spota, and is represented at figure 183, plate 6. MICROSCOPE IN-DOORS. 91 As one of the hard parts of animals, tlie struc- ture of cartilage is very interesting. A slice may be obtained from the gristle of any young animal. Its structure is best seen in the mouse's ear, repre- sented at figure 231, plate 8. No one who looks at this object can but be struck with its resemblance to vegetable tissue ; and it was this resemblance which led to the application of the cell theory of development, which had been made out in vegetable structures, to those of animals. Many of the soft parts of animal tissues aflPord instructive objects under the Microscope. If the tongue is scraped, and a drop of the saliva thus procured placed under the Microscope, it ^ill be found to contain many flat, irregular, scale-like bodies with a nucleus in the centre, such as are seen at figure 4, plate 1. These scales are flattened cells, and closely resemble those found on the surface of the skin. Cells of a difierent kind line the air- passages. If a snip be taken from inside the nostril of a recently killed ox or sheep, it will be found to be composed of cells which are fringed with cilia at the top. These are seen at Figure 5, Plate 1. These cilia are constantly moving, and produce the motion of the mucus on the surface of these passages which is essential to their healthy action. The blood of animals presents us with objects of high interest. The human blood consists of a liquid in which float two kinds of cells. They are discoid bodies, from the three-thousandth to the three- thousand-five-hundredth of an inch in diametei (__i_ to a-^'oo).^ a^^ about a fourth of that size in thickness. They are represented at figure 6, plate 1. They are of two sorts — pale and red ; the latter are rather smaller, but are by far the most abundant. They present a little spot in the centre, 92 A HALF-HOUR WITH THE which is called a nucleus, and this again another little spot, which is called a nucleolus. The red globules vary much in size and form in different animals. Thus, in birds, reptiles, and fishes, they are oval instead of round ; and, mostly, in these three classes much larger than in mammals. This is especially the case in the batracMan reptiles, to which the frog and toad belong. Those from the frog are shown at figure 8, plate 1. In the fowl, shown at figure 7, and in the sole, seen at figure 9, they are nearly twice as large as in man. In the insects they are also frequently of large size, as in the cockchafer, seen at figure 10. The proof that blood-stains have been produced by human blood on articles of dress and other things, is frequently important in medico-legal in- vestigations. Although it cannot be distinguished from all other kinds of blood, it may be from some ; and the Microscope has been employed as an adjunct in such cases. The structure of the skin, and other organs of the body, are very interesting subjects for micro- scopical investigation ; and volumes have been written upon their diversified details. The struc- ture of voluntary and involuntary muscular tissue may be easily examined, especially the former, by taking a portion of the flesh of any animal usually eaten as food. The striated fibrillse of voluntary muscle may be best seen in flesh cooked as food. A muscle consists of bundles of fibres, and each of these fibres consists of several fibrillse lying close together. Each of these fibrils is seen to be crossed with lines, represented in figure 233, plate 8. These lines indicate the point of union of the string of cells which form the ultimate parts of the muscular tissue. The structure of nervous tissue ia also one of MICROSCOPE 1N-D00R3. Vo high interest to the physiologist, but it requires the highest powers of the Microscope, and great skill in manipulation, to make out. We must now, however, draw our last half-hour to a close. All we have attempted has been in the way of introduction. We have only described those things which are most easily obtained, and we have sought rather to create a desire for further know- ledge, than to impart an exhaustive amount of information on any one subject. Those who have properly apprehended our re- marks will see that there is not a distinct science of microscopic objects, but that these objects belong to various departments of science, whose great facts and principles must be studied from works devoted to them. The Microscope is in fact an instrument to assist the eyes in the investigation of the facts of structure and function, wherever they may occur in the great field of nature ; and that inquirer must have a very limited view of the nature of science, who supposes either that the Microscope is the only instrument of research, or that any in- vestigation, where its aid reveals new facts, can be successfully carried on without it. APPENDIX. BY THOMAS KETTERINGHAM. -♦<>•- THE PREPAEATTOX AND MOUNTING OF OBJECTS. The majority of objects exhibited by the Microscope require some kind of preparation before they can be satisfactorily ehown, or their form and structure properly made out. To convince the beginner of this, let him take the leg of any insect, and, without previous preparation, place it under his Microscope, and what does he see ? A dark opaque body, fringed with hair, and exceedingly indistinct. But let him view the same object prepared and permanently mounted, and he will then regard it with delight. That beautiful limb, rendered transparent by the process it has undergone, now lies before him, rich in colour, wonderful in the delicate articulation of its joints, exquisite in its finish, armed at its extremities with two sharp claws equally serviceable for progression or aggression, and furnished, in many instances, with pads {pulvilli) (see plate 7, figures 205, 206), which enable the insect to walk with ease and safety on the smoothest surface. If the beginner has a true love for the study of the Microscope, he will be glad of information respecting the method pursued in dissecting and preserving microscopic objects, nor will he rest satisfied until he has acquired some knowledge of the art. We will briefly point out a few of the advantages possessed by those who are able to prepare specimens for themselves. Objects well mounted will remain uninjured for years, and will contin le to retain their colour and structure in all their original freshness. They can be exhibited at all times to one's friends, and may be studied with advantage whenever an opportunity occurs. 96 APPEXDIX. By the practice of dis«?ection such a knowledge is gained of the varied forms and internal organization of minute creatures as can be obtained in no other way. There are doubtless many who, possessing a small Micro- scope, are unable by reason of their limited means to expend money in the purchase of ready-prepared specimens. To stioh, a few plain directions, if followed, will be of service, and will enable thsm to prepare their own. The materials necessary for the beginner are few, and not expensive. In fact, the fewer the better ; for a multiplic'ty is apt only to cause confusion. The following will be found sufficient for all ordinary purposes, and may be obtained at aay optician's. Bottle of new Canada balsam. Bottle of gold-size. Bottle of Brunswick black. Spirits of turpentine — small quantity. Spirits of wine — small quantity. Solution of caustic potash {liquo)' potassce). Ether — a small bottle. Empty pomatum-pots, with covers, for holding objects while in pickle. Half a dozen needles mounted in handles of camel-hair brushes. Pair of brass forceps. Two small scalpels. Pair of fine-pointed scissors. Camel-hair pencils — half a dozen. Slips of plate-glass, one inch by three inches — two dozen. Thin glass covers, cut into squares and circles — half au ounce. We will suppose that the beginner, having purchased the necessary materials, is about to make his first attempt. Let him attend to the following advice, and he will escape many failures. He must bring to his work a mind cool and collected ; hands clean and free from grease. Let him place everything he may require close at hand, or within his reach. A stock of clean slides and covers must always be ready for use. He must keep his needles, scissors, and scalpels scrupulously clean. An ingenious youth will readily construct for himself a box to contain all his tools. Cleanliness is so essential to success, that too much stress cannot be laid up ^n it. All fluids should be filtered and kept in well-corked phials. A bell-glass, which may be purchased for a few pence, will be fuund exceedingly useful iu covering an object when any delay APPENDIX. 97 takes place in the mounting. For want of it, many specimens have been spoilt by the intrusion of particles of dust, soot, and other foreign substances. Let the table on which the operator is at work be steady, and placed in a good ligh t, and, if possible, in a room free from intrusion. Wings OP Insects. — Perhaps these are the easiest objects upon which the beginner can try his "'prentice hand." Here little skill is required. Select a bee, or wasp, and with your fine scissors sever the wing from its body ; wash it with a camel-hair brush in some warm water, and place it between two slips of glass, previously cleaned, which may be pressed together by a letter-clip, or an American clothes-peg ; place it in a warm corner for a few days ; when quite dry, remove it from between the slides, and soak it for a short time in spirits of tiirpentine. This fluid renders the object more transparent, frees it from air-bubbles, and prepares the way for a readier access of the balsam to the various portions of its structure. Having selected from your stock a clean slide of the re- quisite size, and a thin glass cover somewhat larger than the object about to be mounted, hold them both up to the light, when any slight impurities will appear, and may be speedily removed by rubbing the surfaces of the glass with a fine cambric handkerchief, or a piece of soft wash-leather. Should, however, a speck or flaw in the glass itself be found in the centre of the slide, at once reject it and choose another. Remove the wing with a pair of forceps from the turpentine, and place it in the exact centre of the slide : this may be accomplished by cutting a stiff piece of card- board, tin, or zinc, the size of the slide, and punching a hole, the edge of which should be equally distant from each end and each side ; lay the slide upon it, and place the object in the circular space ; you will thus get it properly centred. Before dropping the balsam (which should have been previously warmed) upon the specimen, place it under the Microscope : you may possibly detect some foreign substance, in the shape of a particle of soot or a fibre from your hand- kerchief, in contact with it ; remove it with the point of a needle. Take up a small quantity of the balsam on the end of a small glass rod, and let it fall upon the object ; hold the slide for a few minutes over the flame of a candle or spirit- lamp at a distance sufficient to make it warm, but not hot ; the balsam will gradually spread itself over and around the object : should air-bubbles arise, they may be broken by touching them with the point of a needle ; they will, how- H 98 APPENDIX. ever, frequently disperse of themselves as the balsam dries. The thin glass cover, being warmed, should now be placed upon the object, and a slight pressure applied to get rid of the superfluous balsam. Place the slide in some warm spot to dry ; an oven will do very well, if the fire has been some time removed and there is not sufficient heat to make the balsam boil. In a short time the balsam round the edges of the cover will be hard enough to admit of the greater part being scraped off with a knife ; the remainder may be got rid of by wiping the slide with a rag dipped in turpentine or ether. The finishing touch consists in labelling the object with its proper name. It will be found advantageous to place the common name of the specimen at one end of the slide, and its scientific name at the other. Some persons prefer covering their slides with ornamental paper, which may be obtained of almost any optician. Others prefer the glass without any covering at all. In the latter case the edges of the slide should be ground, the round thin glass covers used, and the name scratched upon the slide with a writing diamond. In the former, the edges of the slide, being covered with paper, need not be ground, but square thin covers should be used instead of round ones, and the name written with pen and ink in the square places allotted at each end of the slide. Legs of Insects (plate 7, figures 205, 206, 207 ; plate 8, figures 215 to 219, 223, 224. — These require a little more preparation than wings ; and as they possess some thick- ness, and are mostly opaque, besides being of a hard, horny character, they should be placed for a fortnight, or even longer, in liqiwr potasses; this will soften the tissue and dissolve the muscles and other matter contained within them, so that by gently pressing the limb between two slips of glass, the interior substance will gradually escape, and may be removed by repeated washings. The squeezing process, however, must be conducted gently, to prevent any rupture : perhaps the best plan is to plunge the slipa of glass into a basin of clean water, when all impurities oozing out from the pressure will sink to the bottom. Should the leg not be sufficiently softened to be squeezed quite flat, it must be again placed in the solution for a longer period, until this result be obtained. On re- moving it from the potash, it should be well washed with a camel-hair pencil in clean water, placed between two slips, held together by an American clothes-peg with a good stiff APPENDIX. 99 Bpring. If placed in a warm corner, a few days will ba sufficient to dry it thoroughly : afterwards soak it in spirits of turpentine ; the time of immersion to be regulated by the opacity of the object. The directions for mounting in balsam are precisely the same as those given for the wings of insects. Care should be taken not to heat the balsam too hot, as it will invariably destroy delicate specimens by curling them up. In tough horny structures, such as the wing-cases of beetles, &c., heat is sometimes an advantage, and there are a few structures that show to advantage when the balsam has been heated to a boiling pitch ; but for the majority of objects, a gentle warmth is all that is required. Ovipositors and Stings (plate 7, figure 200) are more diflBcult to prepare, and require some amount of dissection before they can be properly displayed. To do this, some degree of skill is necessary, and a knowledge of insect anatomy, which can be acquired only by study and practice. As a rule, all dissections should be carried on as far as possible with the naked eye; when this has been accom- plished, we must then seek the aid of lenses. The object-glasses of one's Microscope are the best that can be used for the purpose. An inch lens will be found especially fitted for the work. A simple JMicroscope, pro- vided with a broad stage, and an arm movable by rack and pinion, for carrying the lenses, is the kind of instrument usually employed. It should be strongly made, and capable of bearing a good deal of rough usage. Dissections may be carried on under the compound Micro- scope ; but we do not think the beginner would succeed, as objects become inverted and motion reversed when seen through this instrument. If, however, it be provided with an erector, this difficulty is overcome by the object being brought into the same position that it occupies when seen by the naked eye. As most dissections are earned on under water, some kind of shallow trough is necessary to contain it : watch-glasses answer the purpose remarkably well. The small white dishes and covers used for rubbing up colours will be found very useful ; also some cork bungs on which to pin the object ; and these last should have their under sides loaded with lead to sink them in fluid. A great many delicate dissections may, however, be made in a drop of water placed on a slip of glass ; but for all objects of large size, the trough, or some similar contrivance, will be necessary. 100 APPENDIX. All insects that have been killed a long time, and whose bodies are hard and brittle, may be softened by immersing them in the solution already mentioned. The sting of the bee, wasp, hornet, and the ovipositors of many flies, especially the ichneumons, are very similar in their structure, and are generally found at the termination of the abdomen, from which they may be obtained by first slitting open the body of the insect with the fine scissors, and afterwards removing the sting by using the scalpel and needles. One or two of the latter should have their points curved, which may easily be accomplished by heating the ends red-hot in the flame of a candle, and bending them with a pair of small pincers. At first sight the sting pre- sents nothing to the eye but a horny slieath, tapering to a point, with a slit broadest at its base and running down the entire length ; within this sheath, on each side, lies a barbed, sharp-pointed spear, in large insects capable of inflicting a severe wound, while the tube in which they are lodged acts as a steadying rod, and as a channel to conduct a virulent poison to the wound. The bag containing the poison is placed at the root of the sting, and is connected by a narrow neck with the sheath. The difficulty in the dissection of the sting lies in getting the barbed points out of the sheath and placing them on each side of it. The following is the method employed by the writer. ^ The sting is placed in potash until it loses some of its rigidity ; it is then transferred to a slip of glass or earthenware trough. The curved needle-points are essential here. With one, hold the object firmly on the stage of the Microscope, insert the point of the other into the opening at the base of the sheath where it is largest, and gradually draw the point down the tube ; this will make the opening wider, and dislodge the barbs ; arrange them on each side of the sheath, place the sting between two glass slips subject to pressure. When dry, soak it for a few days in turpentine, and mount in balsam in the usual manner. A good specimen ought to show the barbs very distinctly on each side of the sheath. It will be found useful to the student to prepare three specimens of this organ : — 1st. The whole abdomen, showmg the position the sting occupies within it. 2nd. The sting with the barbs lying within the sheath. 3rd. The barbs pulled out of the sheath and placed on each side of it. Three such specimens well mounted will enable the student APPENDIX. 101 to study the structure of this curious organ with advan- tage Spiracles (plate 7, figures 212, 213). — These do not re- quire much dissection. They are generally found on each side of the abdomen, almost every segment of which possesses a pair. Excellent specimens are furnished by the dytiscus, bee, blowfly, cockchafer, and silkworm. To prepare them, separate from the thorax the abdominal portion of the insect, and slit it down the centre with the fine-pointed scissors, draw out the viscera, &c., with the curved needles. The air-tubes adhering to the spiracles may be detached by cutting them away with the scissors. Thoroughly cleanse the horny cuticle by repeated washings, spread it out flat between two slips of glass ; when dry, immerse it in spirits of wine or turpentine for a few days, and mount it in balsam. In this manner the whole of the spiracles of an insect, run- ning down each side of the abdomen, will be displayed. Trachea (plate 8, figure 222). — The best method we are acquainted with for obtaining the air-tubes of insects is that recommended by Professor Quekett : — "By far the most simple method of procuring a perfect system of tracheal tubes from the larva of an insect, is to make a small opening in its body, and then to place it in strong acetic acid : this will soften or decompose all the viscera, and the tracheae may then be well washed with the syringe, and removed from the body with the greatest facility, by cutting away the connections of the main tubes with the spiracles by means of the fine-pointed, scissors. In order to get them upon the slide, this must be put into the fluid and the tracheae floated upon it, after which they may be laid out in their proper position, then dried, and mounted in balsam," The best specimens are found in the larva of the dytiscus and cockchafer, and in the blowfly, goat-moth, silkwoi'in, and bouse-cricket. Gizzards (plate 8, figures 220, a, h ; 221, a, 6).— Most of the insects from which these organs are procured being of large size, it will be necessary to secure them to one of the loaded corks by small pins. The dissection should be made in one of the shallow troughs, filled with weak spirits and water. Cut the insect open ; the stomach will float out with the gizzard attached to it, in the shape of a small bulbous expansion of the size of a pea. Insert the fine point of the scissors, and cut it open ; the interior will be found full of food in process of trituration. Empty the contents of the gizzard, and wash it out welj; place it for 103 APPENDIX. a few days in the solution of potash : and, finally, cleans© it with some warm water and a camel-hair brush. Spread it out flat between slips of glass ; when dry, place it in turpentine for a week, and afterwards mount it io balsam. The best specimens for displaying the homy teeth with which the gizzard is furnished are obtained from crickets, grasshoppers, and cockroaches. Palates (plate 6, figures 171, 172, 173, 174).— These consist of a narrow kind of tongue, armed with a series of horny teeth, placed in regular rows. The whelk, limpet, periwinkle, garden-snail, and the snails found in our cellars and aquariums, are all furnished with this peculiar appara- tus, which may be obtained by laying open the body with the scalpel or scissors. It will generally be found curled up near the head, and may be distinguished by its ribbon-like appearance : patience and skill are necessary to extract it from the surrounding mass. When properly cleaned, it may be at once pressed flat and dried between slips of glass. Many palates polarize well when mounted in balsam ; but if not intended for polarization, they should be mounted in a preservative fluid, composed of five grains of salt to one ounce of water. ToiJGUES, Pkobosces, Mandibles, and Antenn^b (plate 7, figures 197, 199, 202 to 204) are amongst the most beautiful objects exhibited by the Microscope. Many of these, besides the ligula, possess several sharp lancets for puncturing the skin of animals from whom they derive their sustenance. To arrange these organs so that each part may be clearly seen, requires a good deal of delicate mani- pulation. It is generally more satisfactory to mount the whole head of the insect. To accomplish this, it must be softened by immersion in liquor potassce for some time, and the interior substance got rid of by pressure. To dry it flat, place it between two slips of glass, which should be held together by a spring-clip ; soak it for a fortnight or longer in turpentine, until it becomes transparent, and then mount it in balsam. The head of the bee, wasp, dronefly, blowfly, and gadfly, are all excellent examples of the varied structures of these suctorial organs. Eyes (plate 7, figures 208, 208a, 210).— The compound eyes of insects, for the display of their numerous facets, should be dissected from the head, and macerated in fluid. The black pigment lining the interior may be got rid of by washing it away with a camel-hair brush. When quite APPENDIX. 103 clean, the cornea may be dried and flattened between two slips of glass. In practice, however, the cornea, from it3 sphericity, will be found to have a tendency to fold in plaits, or to split in halves. To remedy this, cut with the fine scissors a few notches round its edges ; it may then be flattened without danger of its either wrinkling or splitting. When the cornea is very transparent it should be mounted in a cell with some kind of preservative fluid (spirit and water will do very well), otherwise the structure will be lost if mounted in balsam, the tendency of that substance being to add transparency to every object with which it comes in contact. But there are many insects in whose eyes the hexagonal facets are strongly marked : all such will show best when mounted in balsam. Hairs (plate 7, figures 184 to 191). — These may be mounted either in fluid or balsam, first taking the precaution to cleanse them from fatty matter by placing them in ether. If the hair be coarse and opaque, mount it in balsam ; if fine and transparent, it should be mounted in a cell, with some weak spirit. Sections of hair are made by gluing hairs into a bundle, and placing it in a machine for making sections. By means of a sharp knife which traverses the surface, the thinnest elices may be cut, and each individual section afterwards can be separated in fluid. To select the thinnest and best, place them under the Microscope. The point of a camel-hair pencil will be found the best instrument for transferring them to a clean slide. When dry, mount them in balsam, as usual. Some very good sections of the hairs of the beard may be obtained by passing the razor over the face a few minxites after having shaved. Scales of Fish (plate 6, figures 178 to 180). — These dermal appendages may be detached from the skin by a knife ; and if to be viewed as opaque objects, may be dried and mounted with no other preparation than cementing over them a thin glass cover. If intended to be viewed as trans- parent objects, the scales should be properly cleaned, dried, and mounted in balsam ; but the most satisfactory way of exhibiting their structure is to mount them in a cell with some preservative fluid. Scales of Butterflies, Moths, &c. (plate 8, figures 225 to 229), — Select the wing of a living or recently-killed insect, gently press it on the centre of a clean glass slide. On re- moving the wing, numerous scales will be seen adhering to the slide ; place over them one of the thin glass covers, and cement it down by tipping lightly the edges with gold size. 104 APPENDIX. Specimens should be taken from various parts of the wings of the same insect, as the form of the scales vary according to the position they occupy in the wing. Sections or Bone (plate 8, figure 232), — All hard and brittle substances from which thin slices cannot be made by a sharp knife, must be reduced to a transparent thinness by the process of grinding down. Having selected the bone from which the section is about to be made, a thin slice should be cut from it with a fine saw. At first the section may be held by the fingers while grinding down one of its surfaces on a coarse stone ; but when it approaches the thin- ness of a shilling, it must be cemented by some old and tough Canada balsam to a slip of glass. Upon the perfect adhesion of the section to the slide depends in a great measure the success of the operation. Having reduced the thickness of the section by a coarse stone or a file, transfer it to a hone ; a few turns will obliterate scratches, and produce an even, smooth surface, which may be further polished by rubbing it on a buff-leather strop charged with putty-powder and water. When dry, attach the polished surface to the glass slip : this gives a firm hold of the section, which would otherwise become too thin to be held by the fingers. In rubbing down the unfinished surface, take care that an equal thickness pre- vails throughout the section. As it approaches completion, recourse must be frequently had to the Microscope, in order to determine how much further it is necessary to proceed, a few turns either way at this stage being sufficient to make or mar the specimen. When it has become so transparent that objects may be readily seen through it, remove it from the hone and polish it on the strop. To detach it from the slide when finished, place it in turpentine or ether, both being excellent solvents of balsam. Mount in the di'y method, by simply cementing a thin glass cover over it. In recent bone, this method of mounting, though the most difficult, is decidedly the best for displaying its structure. Fossil bone, however, where the interstices are filled with earthy matter, shows best in balsam. Spines of the Echinus (plate 5, figures 151, 152); Sec- tions OF Shell (plate 6, figures 165 to 169). — These are cut and reduced in the same manner as sections of bone ; but they require greater care in grinding, in consequence of being more brittle. The polishing, however, may be dis- pensed with, and the section mounted in balsam. Stones of various kinds of Fruits (plate 8, figure 243) will well repay the labour bestowed in producing good sec- tions. The s&w, the file, and the hone are ths principal APPENDIX. IQo agents used in the reduction of these hard osseous-like tissues. A perfect section should have but one layer of cells, which may be admirably seen when mounted in a cell with weak spirit. Sections of "Wood (plate 3, figures 54 to 59). — To make thin sections of hard wood it will be necessary to employ some kind of cutting machine. There are several of these, more or less expensive, but the principle of construction in aH is similar. The wood, after some preparation, and being cut to the requisite length, is driven by a mallet into a brass cylinder, at the bottom of which works a fine screw with a milled head. The wood is pushed to the surface of the tube, and to any degree above it by the revolution of the screw ; when a sharp knife, ground flat on one side, is brought with a sliding motion in contact with it. The slices may be removed from the knife by a wetted camel-hair pencil, placed in some weak spirit, and examined at leisure ; the thinnest and most perfect section being retained for mounting. Green wood previous to being cut should be placed in alchohol and after- wards in water. Hard and dry wood may be made sutfi- ciently soft for slicing by first immersing it in water for some days. Sections of the above may be mounted either in balsam or fluids. Stems of plants, horny tissues, and many other substances not sufficiently hard to be ground down, may be cut into slices of extreme thinness by this handy instrument. In order to obtain a correct idea of the struc- ture of wood, bone, and shell, sections should be made in vertical, transverse, and oblique directions. Cuticle of Plants (plate 2, figures 42 to 46), Haiks (plate 3, figures 74 to 88), and Spiral Vessels (plate 2, figures 47 to 49), may all be obtained by macerating the leaves and stems of plants in water, and afterwards dissect- ing them with the needles. Good specimens of the cuticle, showing the stomata, may be often obtained by simply peeling ofi' the skin with a sharp knife. Hairs may be de- tached from various parts of a plant by a similar process. Spiral vessels will, however, require to be separated by the needles from the surrounding tissues. All delicate vegetable preparations are best displayed when mounted in a ceil with weak spirit. Cells for mounting objects in fluid are generally formed of some kind of varnish upon which the fluid will not act ; gold-size and Brunswick black are most commonly used. To form a cell, simply charge a camel-hair brush with the varnish, and enclose with a broad black ring a small circular space on the centre of the slide. When quite dry, it is ready 106 APPENDIX. for use. Place the object, with a small quantity of fluid, in the cell ; and having lightly touched the edges of the thin glass cover with gold-size, drop it gently on the specimen ; the superfluous fluid will escape over the sides of the cell, and may be removed by small pieces of blotting-paper, taking care, however, that none of the fluid is drawn from the interior of the cell ; in which case an air-bubble would immediately appear. To make the cell air-tight, gradually fill up the angle formed by the edges of the cover with the cell, by running several rims of varnish round it. In order to prevent the cement from running into the cell and spoiling the specimen, each layer should be dry before another is placed upon it. The student should always have a stock of cells on hand ready for immediate use. Dozens of these cells may be made in half an hour by an ingenious little turntable, the inven- tion of Mr. Shadbolt, and which may be obtained for a few shillings. The limits of this little work have precluded us from giving little more than general directions respecting the l)ermanent preparation of microscopic objects. Our object has been merely to give a few plain instructions, which, if carefully followed, will enable the beginner to prepare some of the most popular objects exhibited by the Microscope. THE END, Fcap. cloth, price 2s. &d. THE PREPAUATION & MOUNTING OF MICROSCOPIC OBJECTS, BY THOMAS DAVIES. CHAPTER I. Apparatus : Glass slides used for mounting — Tliin (ilass Covers — How to clean them — Cutting thin glass — Wooden slides for opaque objects — Shadbolt's Turn- table for making thin cells — Camel's-hair Pencils — Needles— Knives— Scissors — Glass Tubes— Forceps — Watch-glasses— Lamps — Various Cements — Canada Bal- sam— Asphaltum — Marine Glue — Gold Size — Liquid Glue — Black Japan— Electrical Cement — Gum- water — Sealing-wax Varnishes — Black Varnish. CHAPTER IL Mounting objects "dry" : Various processes, ftc, in making thin cells, and securing the thin glass covers — The collecting of Diatoms, and their preservation, cleansing, and mounting — Foraminifera : Methods of obtaining them, with instructions for cleanmg and mounting — Plants, leaves, hairs, scales, cuticle, pollens, and seeds of, mounted dry as opaque objects — Corallines — Scales of Insects — Blood Corpuscles — Ferns and Fungi, spores of — Rbaphides or plant crystals — Scales and spines of fish — Insects. CHAPTER III. Mounting in Canada Balsam — Air-bubbles, how to get rid of— Soaking in Tur- pentine— Hot-air Bath — Chloroform — Air-pump — How to preserve Zoophytes with their tentacles extended — Spicula of Sponges — Preparing and mounting- whole Insects — Eyes — Antennae and feet of Insects— Organs of respiration — Parasitic Insects, Mites, Ticks, &c. — Crystals — Preparation and mounting of various objects for polarized light. CHAPTER IV. Preservative Liquids, &c. : Distilled Water— Glycerine — Deane's Compound — Glycerine Jelly— Goadby's Fluid— Thwaites's Liquid — Chloride of Zinc Solution- Carbolic Acid— Castor Oil — Various kinds of cells used for objects mounted in fluid, with the methods used for attaching them to the sUdes, and cementing the thin covers. CHAPTER V. Sections, and how to cut them, with some remarks on dissection — Cutting and polishing sections of shells— Echinodermata— Corals— Coal, Flmt, Teeth, Bone, Horn, and other hard tissues— Cutting Machine for making thm sections of wood, hair, &c. — Valentine's knife for making sections of soft substances — Instruments used in dissection; how to use them — Vegetable and animal tissues— Muscle — Nerve Tissue— Trachea of Insects— Tongues or palates of Molluscs. CHAPTER VI. Injection Syringes— Stopcock— Curved Needles — BuU-nosed Forceps — Various kinds of coloured injections, their composition, <&c. — A description of the process of injection— The best manner of making treuisparent injections — The best method of mounting injected objects. CHAPTER VII. Miscellaneous : Apparatus for \'iewing the circulation of the blood in the foot of the Frog— Tongue of Frog- Tadpoles, Fishes, Insects, &c.— Curculation of sap in plants— Valhsneria—Anacharis—Alsinastrum — Chara vulgaris— Nitellte, &c. — Unfolding of the spiral fibres in the seeds of plants— Fructification of Fern Fronds —Spores of Equisetacese— Microscopic Photographs. LONDON: KOBERT HAEDWICKE, 192, PICCADILLY. Price 2s. 6d. Illustrated by the Best Artists. THE POPULAR SCIENCE EEVIEW. A QUARTERLY MISCELLANY Of Entertaining & Instructive Articles on Scientific Subjects EDITED BY HENRY LAWSON. M.D., Co.Lecturer on Physiology and Histology, St. Mary's Hospital Medical School; and one of the Lecturers on Natural Science under the " Science and Art Department of the Committee of Council on Education." The Popur,AR Scexce Review is, as its name implies, a Review conveying scientific knowledge in such a simple and popular form, tliat all who read may understand. There is at the present day a numerous and increasing class of intelligent readers who, without being scientific, are nevertheless greatly inter- ested m scientific progress. They would %villingly become acquainted with scientific truths, but are too often deterred from the pursuit of such studies by the abstruse or technical language in which these truths are conveyed. In order to meet the requirements of this portion of the community, every available means has been adopted to procure the most accurate information on all subjects of which the journal treats. No pains or expense has been spared to secure the most skilful artists to illustrate its pages. Each number contains systematic, instructive articles (illustrated when needful) on subjects connected with some ot the following sciences, viz. Astronomy, Geography, Botany, Geology, Chemistry, Metallurgy, Ethnology, Microscopy, t^,. «».., aim Science applied to the Arts, Manufactures, Commerce, and Agriculture. CONTRIBUTORS. Mineralogy, Physics, Zoology, &c. &c., and Adams, A. Leith, M.A., M.D., F.L.S Andrews, W., M.R.I.A. (V.-P. of the Zoological Society of Ireland) . Ansted, Professor, F.R.S., F.G.S. Anstie, F. E., M.D. Beale, Lionel, M.B., F.R.S. Bond, Prof. F., M.B., F.C.S. (Hartley Institute, Southampton). Breen, James, F.R.A.S. BucKMAN, Prof. James, F.L.S. , F.G.S. CoBBOLD, T. Spencer, M.D., F.R.S. COOKK, M. C. Crookes, William, F.R.S. De Quatrefages, Professor. Debus, H., F.R.S. Fairbairn, W., LL.D., F.R.S. Eraser, W., M.D., F.L.S. Gam gee. Professor. Glashikr, James, F.R.S. Gore, George. GossE, Philip H., F.R.S. Hicks, J. Braxton, M.D., F.R.S. Houghton, Rev. W., F.L.S. Hunt, Robert, F.R.S. Jesse, E., F.L.S. Jones, Prof. Rymer, F.R.S. Jones, T. Rupert, F.G.S. King, Prof. (Queen's Coll., Galway). Lankester, E., M.D., F.R.S., &c. Lankester, Mrs. Lewes, George H. Liebig, Baron, Mackie, J. S,, F.G.S. Patterson, Robert, F.R.S. Richardson, B. W., M.A., M.D. Roberts, G. E., F.G.S. Seemann, B., Ph.D., F.L.S., &c. Symonds, Rev. W. S., F.G.S. VoELCKKR, Prof., F.C.S. (Agricultural Coll., Cirencester). Walker, Charles V., F.R.S. Williamson, Prof., F.R.S , ,^ ,„. .......l^..»0<^.v,Xi>Ji., i. IV.tJ. And other Writers who take a prominent part in Scientific Literature. " This is a wonderful half-crown's worth ; its text, as well as its excellent and accurate illustrations, show it to be one of our cheapest and best periodicals. In this its second, as in its first number, it is fully up to the very highest standard fixed by its conductors. We vsrish it every success, and we heartily commend it to such of our readers as take an interest in the various phases of popular sci ence . ' '—Standard. The "Popular Science Review" appears in October, January, April, and July. Price to Subscribers, 10s. per Annum, Carriage Free. LONbON: ROBERT HARDWICKE, 192, PICCADILLY.