The MRI scanner measures this signal difference and displays the activity as a colored area (Figure 1). Diffusion Tensor Imaging (DTI) is a technique that detects how water travels along the white matter tracts in the brain (Figure 2). White-matter tracts connect different parts of the brain and must be protected during surgery. A dye (contrast agent) may be injected into your blood stream.
Dock spiders can swim. A dock spider can actually swim under water and stay submerged for several minutes. It uses air bubbles trapped in the fine hairs on its body under its belly to provide oxygen while it is under water â a bit like a dock spider scuba dive. Dock spiders walk on water.
One of the smallest and most venomous spiders in the world is the black widow spider. The venom in a black widow spider is 15 times more deadly than a rattlesnake, but luckily, the spider will only bite in self-defense. One of the largest dangerous spiders in the world is the Northern funnel web spider. It lives in Australia and can grow to be more than 3 inches long. It lives in trees, is attracted to water and can sometimes be found in swimming pools.