The photographic news

• Bandzählung: 35.1891
• Erscheinungsdatum: 1891
• Sprache: Englisch
• Signatur: F 135
• Vorlage: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: SLUB Dresden
• Rechtehinweis: Public Domain Mark 1.0
• URN: urn:nbn:de:bsz:14-db-id1780948042-189100009
• PURL: http://digital.slub-dresden.de/id1780948042-18910000
• OAI: oai:de:slub-dresden:db:id-1780948042-18910000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

SOME HINTS ON PHOTO-MICROGRAPHY* BY T. CHARTERS WHITE. It is not my intention to inflict on you a long dissertation on the subject of this evening’s discussion, but merely to put my remarks in a more coherent form than I should by simply stating them in a conversational way; and in opening these I wish to direct your attention to one point in which I am personally interested, nor do I wish to claim for myself more than my fair share in the revival of the science of photo-micrography. Those who, like myself, are familiar with the progress of microscopical investiga tions, and have watched and followed their elucidations, have been familiar with the splendid work of Drs. Wood ward and Draper in America, and Drs. Beale and Maddox in this country, done in former times. I am speaking now of between thirty and forty years ago, when work was accomplished which, for clearness of definition and amplification, cannot in our days of elaborate apparatus be surpassed, and that in the face of those physical diffi- culties which optical science has done little to overcome. These difficulties are with us to-day, and in the nature of things must ever continue. I fear it was the appearance of these difficulties which discouraged many in the practice of photo-micrography; nevertheless, others continued in the practice of what must be always a fascinating branch of photography, but whatever was done by different workers in it was not published during the last twenty years—at least, to my knowledge—and it seemed to have reached its ultimatum, and was well nigh dropped out of sight. All who study histology must have felt, as I did, that the diagramatic engravings illustrating books on minute anatomy and of physiology very inadequately, if not in correctly, represented the organs and tissues of which they treated, and from this dissatisfaction on my part I resolved to see if a more correct delineation could not be accomplished by photo-micrography. I therefore set to work, and, having only limited means—or if I had had the means, no suitable apparatus was, at that time, forthcom ing—I made a very primitive, homely “rig up,” for I can designate it by no other name, and succeeded so far that I showed my results to others whom I thought might be interested microscopically, who at first endeavoured to show me that it would never work ; others had tried it and given it up as hopeless, but I did not coincide with their views, and, determined not to be deterred in my convic tions, I persevered and produced more correct representa tions of tissues than found in any text books on histology extant at that time. My example and my results stimu lated others to try what they could do, and by demonstra tions and exhibition of my poor prints at different scien tific societies, others were induced to take up the practice, infected by my example, and soon the revival was in full swing, till now the medical journals contain, in almost every issue, photographic representations of pathological specimens. So far, I am greatly satisfied with the pro gress made since my first paper on this subject appeared in the British Journal of Photography in 1883. Photo-micrographs will henceforth give a more definite view of tissues than was ever the case before ; they will, however, never supersede the microscope and micro scopical observation, for however highly magnified, how ever clearly defined they may appear, none of them will stand examination with an ordinary magnifying glass; * Read at the Photographic Club, January 7th, 1891. they can but indicate to the student the general ap pearances to be looked for, and will be fairly accurate representations drawn by the pencil of light, and free from any bias on the part of the draughtsman. They will also be accomplished in a much shorter time than can be done by the camera-lucida, besides containing also all the elaborations of the most complicated tissue, which fairly defies the capabilities of the most painstaking and care ful draughtsman. To produce these results certain conditions must be observed, which experience on my part, as well as on that of others, has fully confirmed. Perhaps the most important is that the photo-micrographic apparatus must be absolutely steady, and free from the very slightest vibration. There are very few houses in London or any other great town which are sufficiently stable not to be influenced by persons moving about in them, or that are not slightly shaken by tremors arising from the passing traffic, and therefore this tendency to vibration must be neutralised by selecting an operating room in the basement, on as solid a foundation as it is possible to procure. Next, the apparatus itself must be strongly constructed, that no un steadiness exists in its constituent parts. It must be fixed on a firm base-board, so that whatever slight vibration may arise will be communicated uniformly throughout the whole system of light, microscope, and plate. The base-board must also be placed on some elastic support. Various devices have been adopted to accomplish this by different workers with whom I am familiar. One hangs his apparatus on strong india-rubber rings, suspended from strong iron supports let into the wall of his operating room. Another places blocks of india-rubber as feet under his base-board ; others have put bags of cotton-wool under. I find that a bundle of journals placed under each end of the base-board, while firmly and steadily support ing it, serves to break any vibration that may arise, and, notwithstanding many sources of local disturbances, my results show very little, if any, evidence of vibration. Having overcome this difficulty, the next disturbance may arise from another source. Light your lamp, and accurately focus your object, and let things remain for ten minutes ; then look at your object. It will now appear blurred, and considerably out of focus. This arises from the expansion of all the metal parts of the apparatus from the heat of the lamp. Now focus your object again, and in another ten minutes examine it, when probably it may remain as sharp as when you first arranged it, and no further expansion will take place the rest of the evening. The next precaution to be observed is that the light is accurately centred. This is most important, as upon this depends that freedom from diffraction without which it is hopeless to look for sharp definition. The plan to be adopted is simply to put on the microscope a low power objective—say a 1-inch or 14-inch focus—and if a dia phragm with a very small stop is attached to the condenser in the sub-stage, rack the microscope out till the image of the stop occupies the centre of the focussing screen. This may be done by altering the relative position of the lamp to the condenser, but is more perfectly done if the condenser has adjusting screws attached to it. I find that having done this with a low power, if that is superseded by one of a higher grade, such as a } or A, the first centre ing is only approximate, and a further adjustment is re quired, but this is more easily done, having had the pre vious rough adjustment. Too much attention cannot be