On the other hand, don't fall into the widespread delusion that because air is cold it is necessarily pure. Some of the vilest air imaginable is that shut up in those sepulchres known as "best bedrooms," which chill your very marrow. The rheumatism or snuffles you get from sleeping between their icy sheets comes from the crop of bacilli which has lurked there since they were last aired. The "no heat in a bedroom" dogma is little better than superstition, born of those fecund parents which mate so often, stinginess and puritanism. Practically, the room which will _never_ have a window opened in it in winter is the one without any heat.
Similarly, the air in an underheated church, hall, or theatre is almost sure to be foul. The janitor will keep every opening closed in order to get the temperature up. Some churches are never once decently ventilated from December to May. The same old air, with an ever richer crop of germs, is reheated and served up again every Sunday. The "odor of sanctity" is the residue of the breaths and perspiration of successive generations. Cleanliness may be next to godliness, but it is sometimes an astonishingly long step behind it.
The next important step is to keep clean, both externally and internally: externally, by cold bathing, internally, by exercise. The only reason why a draft ever hurts us is because we are full of self-poisons, or germs. The self-poisons can be best got rid of by abundant exercise in the open air and plenty of pure, cold H2O, internally and externally.
Food has very little to do with these autotoxins, and they are as likely to form on one diet as another. In fact, they form normally and in states of perfect health, and are poisonous only if retained too long. It is simply a question of burning them up, and getting rid of them quickly enough, by exercise, with its attendant deep breathing and perspiration. The lungs are great garbage-burners. Exercise every day till you puff and sweat.
A blast of cold air suddenly stops the escape of these poisons through the skin and throws them on the lungs, liver, or kidneys. The resulting disturbance is the second commonest form of a "cold," and covers perhaps a third of all cases occurring. This is the cold that can be prevented by the cold bath. Keep the skin hardened and toned up to such a pitch that no reasonable chill will stop it from excreting, and you are safe. Never depend on clothing. The more you pile on, the more you choke and "flabbify" the skin and make it ready to "strike" on the first breath of cold air. Too heavy flannels are cold-breeders, and chest-protectors inventions of the evil one. Trust the skin; it is one of the most important and toughest organs in the body, if only given half a chance.