A first look at the small world

In 1665, the Englishman Robert Hooke published an amazing book called Micrographia that contained some of the first peeks at a world that was too small to see with the naked eye.

Micrographia, published when Hooke was 30, was the first publication of the Royal Society of London, and the first scientific best-seller. The diarist Samuel Pepys called it "the most ingenious book that I ever read in my life."

Hooke made the illustrations himself, based on what he had seen through a microscope he had built. Looking at a slice of cork, he saw divisions that reminded him of monks' cells in a monastery, and that is what he called them, "cells."

Cork drawing by Robert Hooke

Robert Hooke's drawing of cork cells

Hooke was born on the Isle of Wight, home-schooled and then apprenticed as an artist. He went on to Oxford at a time of unprecedented scientific activity, and he impressed his teachers with his ability to design and execute experiments: He built the vacuum pumps for Robert Boyle, who would demonstrate that gases all act in more or less the same way.

Hooke himself described how springs work in a treatise that gave rise to "Hooke's law" of elasticity. He was also an architect, and worked to help rebuild London after the Great Fire of 1666.

Hooke would probably be more famous than he is had he not quarreled with Isaac Newton over some of their overlapping discoveries. When the scientific community took sides in the dispute, Hooke was shunted aside.

His writings on fossils showed amazing rigor and originality. In the face of a scientific community that considered fossils a "sport of nature," Hook argued correctly that they were the remains of extinct organisms.

Image from Wikimedia Commons

The heart of the matter

The circulatory system is all about distributing oxygen around the body. The mighty heart — which never rests as long as we live — the 60,000 miles worth of blood vessels, and blood itself, all come down to this: Every cell in our bodies needs a fresh supply of oxygen every few minutes, or it will die. And so will we.

Diagram of the human heart

The human heart

The heart is at the center of the circulatory system, a hollow organ composed of muscle and connective tissue. In humans, the heart has four chambers — two atria or "entrances," and two ventricles or "bellies" — and weighs less than a pound.

The heart beats optimally about 70 times a minute throughout our lives, beginning within three weeks after conception, for a total of about 3 billion pulses in a lifetime of  80 years.

The heart pumps blood to the lungs, where it picks up its cargo of oxygen, and then on to the rest of the body.  Valves in the heart and the blood vessels ensure that blood travels in one direction only, away from the heart in the arteries, and toward the heart in the veins.

Red blood cells travel single-file through the capillaries, the fine vessels that connect the arteries and the veins, to deliver oxygen and other nutrients to the cells. Here the blood takes on waste, especially carbon dioxide, which it will deposit in the lungs for expulsion into the air.

A septum in the middle of heart keeps waste-filled blood returning from its journey through the body separate from oxygenated blood fresh the lungs.

Here in the heart, over and over, the journey begins again.

Image from http://commons.wikimedia.org