Relative Sizes of Structures in the Brain

Linear measure- ments and dimensions generally are given in microns or micrometers (µm) (1 µm equals one- millionth of a meter) or nanometers (nm) (1 nm or millimicron equals one-billionth of a meter). About 240,000 µm equal one inch. As a reference, the following are the dimen- sions of some non-neural structures: human ovum, 100 µm; cross-section of a skeletal muscle fiber, 10-100 µm; erythrocytes, 8–10 µm; bacteria, 0.1–8 µm; and viruses, 0.15–0.5 µm. Cell bodies of neurons...

 With Warm-Bloodedness Comes Freedom

Pelorat said, "Tortoises are cold-blooded. Terminus doesn't have any, but some worlds do. They are shelled creatures, very slow-moving but long-living.” "Well, then, isn't it better to be a human being than a tortoise; to move quickly whatever the temperature, rather than slowly? Isn't it better to support high-energy activities, quickly contracting muscles, quickly working nerve fibers, intense and long-sustained thought-than to creep slowly, and sense gradually, and have only a blurred a...