Doses are difficult to control because of individual lung capacity’s
When we breathe, oxygen gets into our bodies. Every day about 2,000 gallons of circulating blood travel through an estimated 60,000 miles of blood vessels<span> which link all the cells and organs of our body.
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The respiratory system is made up of organs and tissues that help you breathe. The main parts of this system are the airways, the lungs and linked blood vessels, and the muscles that enable breathing.
Smallpox<span> vaccine, the first successful vaccine to be developed, was introduced by Edward Jenner in 1796. He followed up his observation that milkmaids who had previously caught </span>cowpox<span> did not later catch </span>smallpox<span> by showing that inoculated</span>cowpox<span> protected against inoculated </span>smallpox<span>.</span>
