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On Exhibit: a menagerie of microscopic monsters



If you were one of those kids who dreaded an errand into a dim, dank basement and who ran back out three steps at a time, sure there was something horrid hiding in the gloom--you were right. Scoffers should take in the "Microspace" show at the Chicago Academy of Sciences, an exhibit of photographs taken through a scanning electron microscope, or SEM.

It's true that the horridness of these basement creatures may not be apparent to the naked eye. But magnify the face of an ordinary ant 230 times and you have a one-and-a-half-foot-wide helmet of a head that's covered with whorls of short bristles, and that's split nearly in two at the jaw. Or blow up the head end of a tick 320 times life size and you'll find little that resembles a head. Only jointed legs wrapped in thick plates where they stick out of a wrinkled mass. At one end of the mass is a crumpled knob, in the center of which is a large maw. Or swell the head of a mosquito 620 times. What first appear to be eyes in the middle of that head--two doughnuts covered with flattened hairs--are actually the bases of its antennae. Below these antennae, a rounded flap hangs over all you can see of its bloodsucking stinger, a buckled straw apparently supported by a channel that is thick with scalelike excrescences. Step back and you see that almost the entire head is one of two enormous symmetrically segmented eyes.

You can see quite well what you might rather not in these large SEM images. Unlike the familiar light microscope, which only allows you to look at a thin slice of, say, a fly's leg, the SEM can let you see the whole thing.

In preparation for SEM viewing, a dead fly, or whatever, is placed in a special argon gas chamber, where it is coated with an extremely thin layer of gold or gold and platinum. The coated fly is then placed under the microscope.

Electric current heats a thin wire at the top of the SEM to 2500 degrees centigrade, forcing a stream of electrons out of it. Strong magnetic fields concentrate that beam as it heads toward the fly. The electrons in this beam bang into the various angles of the fly, knocking off other electrons, which are then picked up by a monitor and converted into the image we see.

While a light microscope can magnify an object only 1,000 to 2,000 times, an SEM can magnify it clearly up to 100,000 times. A fly's leg at 540 times normal size looks simply hairy. At 31,400 times, those hairs become bent spoon handles.

In fact, it is these multiple magnifications of single objects that make these photographs irresistible. The closer you get to the elements of a living thing, the more awesome it is that they do what they do. An eye, after all, is an eye. An eye sees. The moth's eye that we see in this show at 600 times normal, while clearly divided into a honeycomb of domes, is still a comprehensible whole, still an eye set in a face. At 4,900 times, we see only long rows of the domes; the face is gone. At 17,600 times, we see only five of these domes. Once seemingly smooth, the surface of each is now itself broken into an irregular pebble pattern. At 300,000 times, we see only a very fuzzy image of a large number of these pebbles, but can still see that they, too, are further split into smaller spheres. How does anything see through this?

The "Microspace" exhibit will be at the Chicago Academy of Sciences, 2001 N. Clark, through June 6. (There are, of course, photos for the squeamish: a butterfly's wing, the underside of a leaf.) Hours are 10 AM to 5 PM; normally admission is $1 for adults, 50 cents for children and senior citizens, but through January 16 a donation of a can of food gets you in free.

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