Biomedical Engineering Reference
In-Depth Information
Figure 1.11
The snail protects its soft body with a hard-shell which it carries on its back when safe.
which creatures can completely close the shell as a means of defense against predators. While the
snail is able to emerge from its shell and crawl as it carries the shell on the back (Figure 1.11), the
turtle lives inside its ''body armor'' and is able to use its legs for mobility when it is safe and hide its
legs and head when it fears danger. The turtle was probably a good model for human imitation in
terms of self-defense. The idea of body protection was adapted by humans many thousands of years
ago in the form of hand-carried shields that allowed for defense against sharp objects, such as knives
and swords. As the capability to process metals improved, humans developed better weapons to
overcome the shield and therefore forced the need for better body armor in order to provide cover
for the whole body. The armor that knights wore for defense during the Middle Ages provided
metal shield from head to toe. Figure 1.12 shows such an armor for the upper part of the body.
In Japan, a more flexible armor was produced that consisted of thin metal strips connected with
flexible leather bands. Relying on such protection led to defeat when faced against soldiers with
rifles. As weapon technology in the West evolved, efforts were made to reduce the use of armor on
individual soldiers for the sake of increased speed and maneuverability, as well as to lower the cost
of fabrication and operation. In parallel, armored vehicles, which included tanks providing mobile
shield and weaponry, with both defense and offense capabilities were developed. In nature, the use
of shell for body protection is limited mostly to slow moving creatures and nearly all of them are
plant-eaters.
1.5.4.3 Hooks, Pins, Sting, Syringe, Barb, and the Spear
Most of us have experienced at least once in our lifetime the pain of being hurt by a prick from
plants — sometimes from something as popular and beautiful as the rose bush. Such experience can
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