Two-thirds of all colds are infectious, and due, not to cold pure air, but to foul, stuffy air, with the crop of germs that such air is almost certain to contain.

They should be called "fouls," not "colds." They spread from one person to another; they run through families, schools, and shops.

They are accompanied by fever, with headache, backache, and often chills; they "run their course" until the body has manufactured enough antitoxins to stop them, and then they get well of their own accord.

This is why so many different remedies have a great reputation for curing colds.
If you "catch cold," stay in your own room or in the open air for a few days, if possible, and keep away from everybody else.

You only waste your time trying to work in that condition, and will get better much more quickly by keeping quiet, and will at the same time avoid infecting anybody else.