The Bottom Line

To be successfully shrunk, either as a bee or a device, and to still go on working, increase your surface-to-volume ratio. Internal organs or parts of devices extend surface areas relative to a system's volume. Lungs increase surface area for the exchange of gases; the circulatory system distributes material to an internal space that cannot be reached by direct diffusion from the external surface of large organisms; intestinal vili increase the surface area available for intestinal absorption. A tapeworm that lacks a circulation, may be twenty feet long, but a worm may not be thicker than a few millimeters, because food and oxygen have to diffuse through the skin to reach all the cells of its body.

Gravity's relative weakness at insect sizes permits insects to have thin, external skeletons permeable to many molecules. The disadvantage of wearing a corseting cuticle is that it enables growth only when sloughed and a new one forms to accommodate an enlarging body. Between shedding and regrowth of cuticles, the insect body remains soft. Were mammals to do away with their skeletons, even for a short time to change skins, the organs of mammalian bodies would collapse under gravity. Lobsters and crabs can grow larger than insects do in air, because water buoys them up so these arthropods spend their 'soft' stages nearly weightless.

Large terrestrial organisms, all in all, resemble each other by having thick legs and relatively short, stout bodies. The "invention" of building internal organs so that they increase their surface areas, helped animals over time to retain their highly successful simple exterior shapes to house large internal volumes. The principle of maximizing surface to volume ratios is important for the nesting of functions on surfaces within devices. Limits may be expanded, but these laws still operate. No Gothic church may be higher than it is long, and no large animal may dip in its middle like a dachshund.

Chapter nine

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