THE PENETRATING EYE

this leader is provided to permit the projectionists to complete adjustments before the film begins the volume and tone are identical to the soundtrack which follows this is a recent photo of a second-year medical student it conveys a good deal of useful information but it fails to tell us that she's a pretty girl that fortunately takes three dimensions which is the way we see the way we comprehend the way we think in the same way we need an instrument that can give us a comparable insight into the microscopic world that briefly is the reason for the scanning electron microscope [Music] [Music] Anna can easily distinguish the red blood cells by size and shape but the image is only in two dimensions as flat as a drawing on a sheet of paper this same blood smear in the scanning electron microscope produces these unique images of red blood cells the preparation of a blood smear for examination on the scanning electron microscope is fairly rapid and simple first the slide is put into a vacuum evaporator where it is coated with a very thin layer of gold no more than a couple of hundred angstroms thick biological materials conduct rather poorly this treatment makes the surface electrically conductive so it's ready to be scanned by the moving electron beam of the scanning electron microscope the whole slide not just a tiny fragment of it is inserted into the airlock chamber the position of the slide can be observed through an airtight port in the column of the instrument so it can be checked and adjusted the whole process generally takes about two minutes now we are ready to look at the sample of Anna's blood on the face of a cathode ray tube we see the result of this new method of imaging a third dimensional view of Anna's blood smear as with any microscope what we see can be photographed and recorded we feel we're in contact with the real thing because we see form as we are accustomed to see form in the familiar parameters of size shape texture and depth if greater magnification is needed one has only to turn a knob up to a limit the form of the normal red blood cell is quite stable and this biconcave pseudo donut is probably much like the shape of the cell in the human bloodstream the same is not quite true for more fragile specimens like the eosinophil for the original shape has been flattened out by drying in the air but when the membrane shrinks we can see the granules inside as here from a patient with leukemia we are only at the beginning in the present state of the art to connect the precise shape of the cell with the disease this kind of red cell the target cell is often found in cases of thalassemia other bizarre cells are also found in patients with this blood disease this form is characteristic of sickle cell anemia here are the strange shapes of red cells after cold agglutination in patients with a campus psychosis here is a whole human blood clot which has been fixed in formaldehyde for 48 hours now we have some idea at a glance of what a blood clot is really like we can make out individual red cells and meshed in bands of fibrin of course we're still looking at the surface how can we look inside one possible way is to blast away the membrane with a beam of ions such as argon or oxygen this cell has been etched in hydrogen for 15 minutes this one for 35 minutes the membrane has been blasted away so we can see what seems to be the structure underneath the scanning electron microscope does not replace the conventional electron microscope or the light microscope but rather offers in addition to our efforts to image biological system for example a nerve tissue culture appears like this through the light microscope however by putting together a mosaic of us from the scanning microscope we can see whole sections of the culture in three dimensions the neurons were there long processes a kind of map in high relief which our minds can immediately grasp and understand precisely because we are Walker's touchers seers in a three-dimensional environment the scanning electron microscope gives us gulliver's some insight into the lilliputian universe the eye is a window from which we view the passing world suppose we turn our instruments around and examine this marvelous organ at first sight it looks like an unknown planet but we are looking at inner space the epithelial cells of the human cornea the outer cells are flat and transparent and air drying has emphasized the junction of cell with cell here for comparison is a part of a rabbit cornea experimentally infected with herpes simplex virus this egg like mass is not the virus but the infected deeper cells of the cornea now exposed deep in the ocular structure of the human is the trabecular meshwork the complex filter through which the aqueous humor flows allowing for the effects of preparation we can see the network of collagen fibers and the thin cells stretched between them the familiar view of a diabetic retina through the ophthalmoscope reveals a great deal of information the scanning electron microscope view gives additional information about the structure of the micro aneurysm and here is a living human eye property of a non diabetic second-year medical student she's interested in the eye of the tribolium the common flower beetle this small creature can be examined in the scanning electron microscope while alive because it has the unique ability to survive in a vacuum for about an hour like most insects it has a compound eye it also has an array of spines among the visual units we can understand this arrangement at once immediately intuitively what we can begin to grasp is the functioning of part with part the connections the architecture of living tissue how does this new instrument work unlike the light microscope and the conventional electron microscope the scanning electron microscope does not form an image by means of a lens in the light microscope light passes through a more or less transparent specimen and then through curved glass lenses in order to produce a magnified image of the specimen can be viewed directly by eye or can be recorded on a photographic plate in the range where the light microscope produces useful resolution the information content of the images is very good generally the size shape and many architectural and chemical relationships can be determined and of course many living objects can be studied too but the light microscope has a useful magnification of at most 1500 times in the conventional electron microscope the image is formed by passing a beam of electrons through the specimen and then using magnetic fields as lenses to focus the electrons the magnified image is visible on a fluorescent screen or the electrons may be allowed to fall directly onto a photographic plate magnification of up to 200 thousand times is common because the image is produced by the conventional electron microscope are not within the mould in which we generally experience the world a considerable amount of interpretation and technical skill is necessary in order to extract useful information from them here for example is a wire mesh 200 square holds to the inch photographed through the conventional electron microscope it looks like no more than a flat shadow but through the scanning electron microscope it's clearly a piece of woven material the quality of woven this is apparent in the third dimensional appearance which the scanning electron microscope can give us at once here is the java rotifer as it is seen by the three methods of imaging essentially the scanning electron microscope is composed of two systems the probing system into which the specimen is placed and the imaging system which displays the visual image in the probing system a hot filament generates a stream of electrons the electrons pass through a hole in the anode is a high velocity beam and are focused on the specimen as a point about one millionth of an inch in diameter at the point where the beam hits the electrons excite the material of the specimen to produce many kinds of radiation including visible light infrared x-rays and streams of electrons a suitable detector is used to measure one particular kind of radiation leaving any one point on the specimen at any one instant one of the most useful kinds of radiation is called secondary electrons the measure of the number of secondary electrons leaving a point on the specimen is used to modulate a second synchronous beam of electrons which is directed to the face of a cathode ray tube resulting in a point of visible light when the induce team high from a point on the specimen the corresponding point on the cathode ray tube display is bright when the beam of electrons is moved to another point on the specimen radiation is induced from that point this information can be displayed in a point adjacent to the first on the face of the cathode ray tube the movement of both beams in synchrony is accomplished by a device called a scan generator as the electron beam moves across each point on the specimen corresponding points are visualized on the display screen of the cathode ray tube in practice the beam moves from point to point rapidly and the series of points becomes an image of a line across the specimen the specimen is scanned by the electron beam so that these lines follow one another rapidly any portion of the specimen scanned by the beam will be visualized on the cathode ray tube the scanning electron microscope can magnify up to 20,000 times to obtain magnification the points and lines formed by the probing beam are packed closer to each other so that only a portion of the specimen is scanned suppose we show you as a kind of scientific game some of the revelations of scanning electron microscopy and give you a couple of seconds to guess the answers can you identify this no it's not it's the New York Times try this no it's not a cactus it's a grain of pollen yes this is the spirochete of syphilis Treponema pallidum and this bizarre organism is a platelet imaged from a smear of normal human blood this looks like an archaeological dig it's an eye on edge piece of tooth enamel showing the various layers as they are excavated for study this is part of the dental picture - it's a plaque scraped from the enamel wall and the spheres are one kind of bacteria not yet identified found an association with human teeth and this is another filamentous kind of bacteria from a carious lesion ecoli the normal guest of the human colon yes this is the same organism but after 90 minutes of exposure to penicillin the sight of what escaped through the damaged cell wall in the presence of higher concentrations of penicillin a bulbous sac develops at the mid portion of the wall this outpouching is apparently the start of the development of an L form or Sphero Plast a stage with a membrane but no wall in this field we see the full progression of the conversion of e.coli to L form organisms in the presence of high concentrations of penicillin first the cells elongate there are extrusions from the damaged wall the formation of L forms the membrane collapses these are cancer cells from a breast cancer the significance of this configuration is not yet known but this is not pathological its neuronal tissue taken from a marine mollusk the knobs are probably neural processes related to the synaptic Junction they have a topography very difficult to see by any other imaging method here are penicillin resistant Staphylococcus I in the presence of penicillin they appear normal but in the presence of the antibiotics f11 the bacterial swell and show granulations and protrusions of the cell wall the full possibilities of the scanning electron microscope are still being explored for example this image of the flower beetle may be modulated by assigning a particular color to a particular intensity thus getting a color image not a color picture since we are not dealing with visible light but a kind of colored diagram like staining which greatly increases the amount of subjective information because finally we see not with instruments not even with our eyes but really with our brain with our whole life experience for the imaging of much biomedical material the light microscope is still most useful for extreme magnification the conventional electron microscope is unsurpassed it has brought us this picture of what may turn out to be the double helix of DNA but for the marvelous individual geometry of life as in this view of the rods and cones of the retina of a salamander the scanning electron microscope remains a true and penetrating eye [Music] [Music] [Music] [Music] [Music]