UIHistories Project: A History of the University of Illinois by Kalev Leetaru
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Repository: UIHistories Project: Board of Trustees Minutes - 1882 [PAGE 104]

Caption: Board of Trustees Minutes - 1882
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98 tinct color of the organisms themselves or to the chemical combination which they produce. The different kinds of Bacteria vary in shape from spherical to oval, fcylindrical and thread-like; and the latter are straight, or crooked, or spiral, flexible or rigid. The spherical ones are often connected in two's or more, and sometimes form bead-like strings or chains. The main classifications in use are based on the form and size of the organisms. It was impossible to know anything about Bacteria until after the invention of the microscope, because none of them can be individually seen with the unaided eye. In transverse diameter, one twenty-five thousandth of an inch is a very common measurement, while some, including spherical ones, are even less than half this size. Now, a dot one two-hundredth of an inch across is barely visible to the eye of most persons, hence a magnifying power of more than one hundred times across (ten thousand in area) is required to barely see a common sized Bacterium. To make out its real shape and any details of structure, ten times the enlargement mentioned is necessary, and not unfrequently as much more as can be secured by the highest possible powers of the microscope. Increase the heighth of an ordinary man one thousand times and his head would be over a mile above the earth, yet under the same magnification one of these organisms would have plenty of room to swim freely, to stand on end and dance up and down, in the film of water included between two pieces of flat glass pressed so close together as to strongly adhere by capillary attraction. From one hundred to twro hundred and fifty of them placed side by side would be required to stretch across the ordinary thickness of book paper. They are the smallest living organisms known to man, yet. as we shall see, by no means the least important in the economy of nature.

3. MOVEMENTS.

Bacteria have sometimes been divided into groups upon their apparent ability to move or not; but further study has demonstrated that many, if not most, species have states in which they remain at rest, and others in which they are freely motile. These states depend partially on their stage of development, partly on the surrounding conditions. For the latter the degree of moisture and temperature, and the food supply, are especially effective. Some species at most only oscillate and quiver in the fluid medium in which they grow, never making progress in any given direction; others slowly and smoothly glide along in a straight but more often undulating path, while still others whirl and dance and roll, turning over and on end, now spinning round and round, now , swaying gently back and forth, now darting like a flash across the microscopic field. Sometimes they move as though perfectly free and had abundant muscular force, at other times they appear to be struggling to overcome obstructions, or to free themselves from some impediment. Not unfrequently they may be seen to carry along little adhering extraneous particles, well showing their vital power, or two, in some way attached, pull in opposite directions with varying advantage for the one or the other.